Holding Pattern

A holding pattern is a standardized oval flight path — resembling an elongated racetrack — that aircraft fly to remain in a defined area of airspace while waiting for a clearance to proceed, typically because the destination airport is at capacity, weather is temporarily below landing minimums, or a sequencing conflict exists in the arrival stream.

What Is a Holding Pattern?

ATC assigns aircraft to holding patterns when more traffic exists than can be accommodated in the approach sequence. The holding pattern is defined by a fix — a geographic point identified by a navigational aid, GPS waypoint, or intersection — and by four parameters: the inbound course (the direction of the inbound leg toward the fix), the turn direction (standard right-hand turns or non-standard left-hand turns), the leg length (either a time-based standard of one minute below 14,000 feet or one and a half minutes above, or a DME distance), and an altitude. When assigned a hold, the crew flies to the fix, turns in the specified direction to intercept the outbound leg, flies the outbound leg, makes a 180-degree turn to re-intercept the inbound leg, and passes over the fix again to complete one circuit. The pattern repeats until ATC issues an "expect further clearance" time and eventually a clearance to leave the hold and continue the approach.

How It Works in Practice

The geometry of a holding pattern is designed for instrument flight in turbulent conditions: the legs are straight enough to maintain instrument accuracy, and the turn radius is controlled by bank angle limits (typically 25 degrees or 3 degrees per second, whichever is less) established in ICAO Annex 6. Published holding patterns at busy airports are depicted on approach charts with the fix location, inbound course, and turn direction clearly shown. At high-traffic airports like Chicago O'Hare, London Heathrow, or Tokyo Narita, aircraft can be stacked in multiple holding patterns at different altitudes above the same fix — a vertical stack — with the lowest aircraft released first and the ones above descending to fill the vacated slot. A significant weather event can result in 30 or more flights simultaneously in holding stacks at different approach fixes around a major hub, burning hundreds of thousands of kilograms of fuel collectively while waiting for the airport to reopen.

The ICAO standard holding speed limits are 200 knots below 14,000 feet, 230 knots between 14,000 and FL200, 240 knots between FL200 and FL340, and the published speed for a specific procedure above FL340. These limits exist to ensure that aircraft do not fly outside the published protected airspace of the holding pattern, which has been calculated based on obstacle clearance.

Why It Matters

Holding patterns are a fundamental capacity management tool. Without them, ATC would be forced to turn aircraft around far from the destination or deny departure clearances from origin airports — both of which create far more disruption than a holding delay. From a fuel perspective, holding is costly: a narrowbody aircraft burns approximately 2,000 to 3,000 kilograms per hour in a holding pattern, which directly converts to passenger delay costs and environmental emissions. Extended holds caused by Heathrow's periodic fog events or JFK summer thunderstorm activity are among the most significant sources of individual flight delays in the global system.

ICAO and FAA have worked to minimize holding through Traffic Management Initiatives (TMIs): ground delays at the origin airport (Ground Delay Programs) substitute for airborne holding by keeping aircraft at the gate burning no fuel until there is a slot available at the destination. When ground delays are impractical — for flights already airborne on long transatlantic crossings when the weather deteriorates at the destination — airborne holding remains the only option.

Key Facts and Figures

• A typical holding pattern circuit takes approximately four minutes at standard speeds below FL140.
• The FAA-published holding airspace at a fix is designed to protect a protected zone accounting for wind drift of up to 56 knots and instrument error.
• London Heathrow has dedicated published holding stacks at five fixes (Bovingdon, Lambourne, Ockham, Biggin, and Mayfield) that regularly fill during periods of reduced airport capacity.
• The Guinness World Record for the longest commercial holding delay is disputed, but documented cases of aircraft holding for more than two hours in fuel-critical situations have triggered emergency declarations.
• Continuous Descent Operations (CDO) and Performance-Based Navigation (PBN) approaches reduce the need for holds by enabling sequencing at the terminal area level without the traditional stack structure.
• FAA Order 7110.65 (Air Traffic Control) dedicates an entire chapter (Chapter 4-6) to holding instructions, illustrating the operational importance of the maneuver.

Related Concepts

ATC, Stack, Ground Delay Program, Approach, Instrument Landing System