There are a few key reasons why planes make turns before landing at an airport. The main reasons are to properly align with the runway, lose excess altitude, and provide spacing between other air traffic. Let’s explore these reasons in more detail.
Aligning with the Runway
The most basic reason planes need to turn before landing is to line up properly with the runway. Runways are long, narrow strips of pavement that planes use to safely take off and land. They are precisely oriented to account for local wind patterns and geography. Planes must approach the runway in a straight line parallel with the runway heading to land safely and smoothly.
As planes approach an airport from their cruising altitude and begin their descent, they are rarely perfectly aligned with the runway. Air traffic control will provide vectors, or heading and altitude changes, that efficiently guide each plane from its cruising altitude and route to the proper runway approach path. These vectors result in a series of turns that line up the aircraft for landing.
For example, a plane approaching from the north may need to make a series of left-hand turns as it descends to align itself with a west-facing runway heading westbound. Timing these turns allows the aircraft to roll out of its last turn lined up with the runway centerline just as it reaches the proper altitude for its final descent.
Losing Excess Altitude
Another reason for the turns before landing is that they provide an efficient way for the aircraft to lose altitude. Commercial aircraft approach airports at very high altitudes, often around 30,000 feet above ground when arriving from longer flights. However, most commercial runways are situated just a few hundred feet above the surrounding terrain.
A plane cannot safely descend directly from 30,000 feet to just a few hundred feet to land. It needs to gradually lose that altitude in increments both to avoid negative effects on passengers from steep descents and to ensure it reaches the proper landing speed.
Making one or more turns during arrival provides a great way for planes to lose thousands of feet of altitude quickly but smoothly. By turning, the pilot can increase drag. This allows the plane to descend continuously without gaining excessive speed in the descent. Executing a series of turns allows the plane to efficiently descend from high altitude enroute to just a few hundred feet above ground as it turns onto its final approach path to the runway.
Maintaining Spacing from Other Traffic
Lastly, turns help aircraft maintain proper spacing from other air traffic as they sequence for arrival and approach to the runway. Air traffic levels are highest around airports, with many planes needing to land and take off in a short timespan.
Controllers need to properly space landing aircraft to avoid delays and provide safe separation between them. Appropriate spacing is usually a few miles between aircraft on the same approach path. Making small adjustments to the timing and angle of arrival turns allows controllers to fine-tune the spacing between landing planes.
For example, if one aircraft is getting too close behind another on approach, a controller might instruct the trailing plane to make an additional turn to delay it getting lined up on the runway by a minute or so. This helps safely space the traffic without excessive slowing or speeding up after the turns are complete.
Standard Arrival Routes
Air traffic control procedures around major airports are complex and standardized. The routes planes follow when arriving to the airport are called standard terminal arrival routes (STARs). STARs including a standardized set of waypoints, altitudes, and legs that planes follow to transition from the enroute phase to beginning their approach to landing.
These routes include predetermined turns at waypoints that serve the purposes of aligning the aircraft with the runway, allowing descent, and spacing with other traffic. Controllers may still provide additional vectors to fine tune an aircraft’s specific path within the STAR. But the established legs, altitudes, and waypoints of STAR procedures form the framework of the arrival turns.
For example, a STAR into Chicago O’Hare Airport may start at a waypoint northwest of the airport at 15,000 feet altitude. It may have aircraft fly direct to a point west of the airport, then make a 90 degree left turn southeast bound. This allows aircraft from various enroute points to merge onto a common intermediate approach leg lining them up for landing southbound on the parallel runways.
Constant Adjustments for Each Flight
While STARs provide a fixed framework for arrivals, controllers still need to tactically vector each aircraft based on current conditions. Things like variable winds, weather, traffic levels, aircraft performance, spacing requirements, and runway changes can all affect how aircraft are navigated from cruise to landing.
The role of air traffic control is to smoothly guide each aircraft within the constraints of the STAR to the proper approach path, taking all these factors into account. The arrivals phase involves nearly constant adjustments being provided to each flight. This results in many turns of varying degrees implemented by controllers issuing heading and altitude changes to set up the optimal path for that specific flight.
Conclusion
Airliners turning to line up for landing is a normal part of arrival procedures at commercial airports. While it may seem complex from the ground, these turns are carefully calculated to position, space, and descend each aircraft for a safe and stable approach to the runway. The turns are choreographed within the structure of standard arrival routes and implemented through instructions from air traffic control.
Next time you see airliners turning overhead as they arrive, you can appreciate the intricacy involved in gracefully transitioning these high-speed aircraft from miles high at hundreds of knots to slow, carefully spaced landings. It’s an elegant aerial dance requiring precision teamwork between pilots and controllers.
Frequently Asked Questions
Why do planes need to lose altitude before landing?
Planes need to lose altitude before landing because they cruise at very high altitudes, typically 30,000 to 40,000 feet for longer flights. Runways are generally only a few hundred feet above the surrounding terrain. Planes cannot descend directly from cruising altitude to runway elevation due to passenger comfort and aircraft handling considerations. Making gradual descents with intermediate level offs allows planes to bleed off thousands of feet smoothly and efficiently on arrival.
Do planes always follow a standard arrival route procedure?
For the most part, yes. Standard arrival routes (STARs) dictate the common legs, waypoints, altitudes, and descent profiles that aircraft use when arriving to land at major airports. However, air traffic control will still provide vectors – customized heading and altitude assignments – to each aircraft within the STAR to properly sequence and space traffic.
When do planes start their arrival turns?
The arrival turns sequence can start hundreds of miles out as planes transition from their cruising altitude and enroute path to begin lining up for landing at the destination airport. The initial turns are designed to take dispersed traffic flows and merge them into a centralized intermediate approach path aligned with the landing runway. Further turns sequence the aircraft into a single-file flow for the final approach segment right before touchdown.
Do pilots or air traffic control direct the arrival turns?
Air traffic control is responsible for providing vectors – the specific altitudes and headings to fly – to aircraft for navigating the arrival turns. However, the pilots physically fly the aircraft to execute the requested turns. Close coordination between pilots and controllers is required to safely manage the high-density traffic flows on arrivals.
Why don’t planes just fly straight in and land without turning?
Flying straight in without turns may be possible when an airport is lightly trafficked. However, at major airports, too many aircraft need to land in a short time period from too many directions. Straight in approaches would create conflicts between landing aircraft. The turns provide an orderly, safe means to sequence and separate aircraft while allowing them to descend, ultimately delivering them to the runway threshold at the proper speed and spacing for landing.
The Arrival Turns Sequence Explained
Let’s walk through the typical sequence of arrival turns executed by airliners coming in to land at major hub airports:
| Phase | Location from Airport | Altitude | Purpose |
| Descent from cruise | 100-200 miles out | 30,000 feet + | Begin gradual descent from cruising altitude |
| Merge onto STAR | 50-100 miles out | 15,000 feet | Transition inbound traffic flows onto standardized arrival routes |
| Intermediate approach | 30-60 miles out | 10,000 feet | Make turns to align with landing runway, continue descent |
| Final approach | 5-10 miles out | 2,000 feet | Execute final turns to align with runway centerline |
The specific distances, altitudes, headings, and legs flown will vary based on the airport, runway in use, weather conditions, and types of aircraft arriving. But this general sequence exemplifies the stepped down descent via turns that brings jets from miles high at hundreds of knots to a slow, stable final approach just feet off the ground and seconds from touchdown.
How Turns Lead to a Stable Landing Approach
Executing the proper sequence of arrival turns is critical for setting up a stable landing approach. A stable approach means the aircraft reaches the final “glideslope” to the runway at the desired speed, descent rate, and configuration.
Factors controllers need to consider when vectoring aircraft to execute arrival turns include:
- Gaining/losing altitude smoothly
- Allowing slower aircraft to stay on speed
- Preventing descending aircraft from gaining too much speed
- Spacing between successive arrivals (miles or minutes)
- Rate of descent on final approach
- Crossing arrival fixes and waypoints at designated altitudes
If any of these parameters are off, it can lead to an unstable approach requiring a go-around and second landing attempt. The art of air traffic control is integrating all these variables to produce a smooth, orderly, positively-controlled arrival sequence via appropriate turn vectors.
Done right, these vectors set up each aircraft to roll out on final approach configured for landing at just the right speed, descent profile, and spacing behind other traffic. The final turns onto the extended runway centerline are the culmination of an intricately choreographed arrival dance designed for safety and efficiency at busy airports.
How Do Controllers and Pilots Work Together?
Close coordination between air traffic controllers and pilots is essential for navigating the arrival turns and approach sequence. Here is the typical workflow:
- Controller provides vectors to aircraft for heading, altitude, and speed
- Pilots read back vectors and fly assigned headings
- Controller monitors radar and makes adjustments as needed
- Pilot requests clearance to descend when ready
- Controller issues clearance for descent
- Pilot descends to assigned altitude and turns to new headings
- Controller sequences aircraft onto final approach course
This exchange continues until aircraft are safely spaced in sequence for landing. Standard phraseology and protocol ensure clear communication. Both parties work as a coordinated team to execute the plan. Smooth arrivals require excellent crew coordination and flight discipline.
How Weather Affects Arrival Turns
Weather conditions can have a significant impact on the arrival turn sequence. Some key weather factors controllers and pilots must account for include:
- Wind: Determines which runways are in use and alters ground speed
- Visibility: May require wider spacing between successive landing aircraft
- Clouds: Could lower allowable minimum altitudes on approach legs
- Turbulence: May require slower maneuvering or speed reductions
- Precipitation: Creates slippery runways and the need for stable airspeeds
- Thunderstorms: Can block arrival routes or create convergence of traffic
Adjustments could include spacing aircraft farther apart, changing altitudes, slowing aircraft, moving approach paths, or even diverting landings to alternate airports. The overarching goal is maintaining safety margins in all conditions.
How Traffic Flow Management Regulates Arrivals
On the national level, the Federal Aviation Administration’s Air Traffic Control System Command Center (ATCSCC) regulates traffic flows based on destination airport conditions. Traffic Flow Management initiatives such as Airspace Flow Programs and Ground Delay Programs manage the pace of inbound flights hundreds or even thousands of miles out when needed.
For example, if storms reduce arrival capacity at Dallas-Fort Worth airport, ATCSCC may put a ground delay program in effect holding planes at their origin airports to properly space flights into DFW. departures
This regulates the flow of aircraft headed to the impacted arrival airport. Planning departuresspacing departures miles from the destination ensures a smooth, manageable arrival sequence when aircraft are vectored for their final turns on arrival. Balancing safety and efficiency at the national level optimizes overall performance of the aviation system.
Trajectory Based Operations
The future air traffic control concept of Trajectory Based Operations (TBO) will further improve the precision of arrival turns. TBO leverages aircraft avionics, ADS-B data sharing, and advanced prediction modeling to define precise 4D trajectories for each aircraft.
This will allow air traffic control to reduce vectoring in favor of more optimized descents computed by the aircraft’s Flight Management System. Aircraft will continuously refine and update Required Time of Arrival (RTA) to key approach fixes based on real-time winds, aircraft performance, and spacing from other traffic.
Less vectoring will be required as automation assists controllers in achieving the optimal continuous descent arrival. This will increase predictability, reduce fuel burn, and minimize noise impacts for communities surrounding airports. Implementation of TBO concepts promises to further streamline and optimize the arrival process at busy terminal areas.
Conclusion
The delicate dance of arrival turns executed by airliners allows them to safely and efficiently transition from high altitude cruise to slow, stable approaches ready for landing. Air traffic control issues precise vectors choreographing the sequence through altitude and speed adjustments. Standard routes and procedures combined with real-time tactical adjustments provide smooth, orderly aircraft flows into congested airports. The next time you see airliners turning overhead, appreciate the skill involved in bringing these aircraft home.