The Trouble With Extended Arrival Management: Pop-Up Flights

The current horizon of air traffic arrival management (AMAN) systems is relatively low for allowing aircraft to absorb delays in an efficient way. The extended arrival management (E-AMAN) concept aims to improve that by extending the horizon. However, this increases the number of flights that ‘pop up’ within the horizon and disrupt arrival planning. It’s a growing issue we need to tackle.

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A Looming Issue For E-AMAN

The AMAN horizon, the set distance around an airport within which incoming flights are managed, is a critical factor in the system’s effectiveness. Airport arrival times are essentially fixed as flights cross the horizon. Extending that horizon would help air traffic control better predict traffic flows, and let aircraft absorb delays more efficiently.

Related blog post on the benefits of E-AMAN

There is, however, a problem with E-AMAN horizons: pop-up flights. Pop-up flights depart within the horizon of the (extended) arrival management system, often negatively affecting the process. Imagine arrival times neatly scheduled for airborne flights that have crossed the AMAN horizon, when a pop-up flight suddenly takes off and needs to merge with existing air traffic. This can disturb arrival planning for multiple flights and trigger schedule revisions.

Impact of Pop-Up Flights

Within the relatively short AMAN horizon of 120 nm, or 225 km, pop-up flights have little opportunity to occur so their impact is small. That changes when the horizon is extended to 200 nautical miles, or 370 km, under E-AMAN. The broader the horizon, the greater the chance of disruption.

Pop-up flights drawing3

The broader the horizon, the more pop-up flights and the greater the chance of disruption.

This topic became the subject of my recent master thesis. Together with my supervisors, Professor Jacco Hoekstra and Asst. Professor Joost Ellerbroek of the Delft University of Technology, and Evert Westerveld of Air Traffic Control the Netherlands, we set up a collaboration project using fast simulation to assess the impact of pop-up flights on E-AMAN.

The research confirmed this looming issue. Pop-up flights do present a clear and negative impact on delay (cost), arrival sequence stability, and flight crew and ATC task load. Chances of disruption from pop-up flights could be expected to increase by a factor of 5, on average, for Europe’s busiest airports. Pop-up flights also tend to occur more frequently during peak periods when ATC is already busy rather than spread out throughout the day, which amplifies the problem.

Amsterdam’s Schiphol Airport, for example, can expect 10% of all arrivals (approximately 70-80 flights per day) to be pop-up flights in the E-AMAN context. Currently, less than 15 flights per day are pop-up flights.

(At the ATM Seminar in Seattle on July 27th, I presented our academic paper highlighting the results. A pdf is available on the ATM website.)

Need For Smarter Algorithms

Pop-up flights are a bit of an unknown quantity. Little information available, but air traffic controllers do recognize the problem. Given the efforts to extend AMAN horizons, it is an issue that deserves more study. After also experimenting with a mitigative measure of pre-planning the pop-up flights prior to their actual take-off, the research clearly suggests we will need smarter algorithms than currently in use for E-AMAN to deal with the uncertainty pop-up flights introduce.

We hope continued research on pop-up flights will help improve arrival management algorithms. It is an exciting and increasingly important development. My colleagues and I at To70 are also working hard – across diverse fields of aviation – to actively develop and integrate advanced algorithms for prediction and uncertainties.

About To70. To70 was founded in The Netherlands in 2000 and has since expanded with offices in Europe, Australia, Asia and Latin-America. Our clients include airports, airlines, governments and air navigation service providers. At to70 we believe that society’s demand for transport and mobility can be met in a safe, efficient, environmentally friendly and economically viable manner. To achieve this, policy and business decisions have to be based on objective information. With our diverse team of specialists and generalists to70 provides pragmatic solutions and expert advice, based on high-quality data-driven analyses.

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