Diversions are rare. A line pilot averages less than one per year, and the flying public might travel a lifetime without ever being part of a diversion. Diversions are always part of the plan but never a desired outcome for an airline. This results in crews and planes being out of position and passengers needing re-accommodation. Diverting costs a lot of money, but pilots and dispatchers do what they can to make the situation financially easy for the airline and streamlined for displaced passengers. Here's an explanation of what pilots think about during diversions. An emergency diversion is different from one required for weather. Emergency diversions are accomplished as directed by QRH checklists or the captain's decision per their emergency authority. At the end of a QRH checklist, an emergency diversion will be indicated by phrasing similar to "land at the nearest suitable airport" or "land as soon as possible." Medical diversions are authorized by dispatch in consultation with doctors who specialize in ground-to-air telemedicine. Contrary to some beliefs, only the doctors employed by the airline's telemedical service, the dispatcher, or pilots can authorize a diversion. A doctor who is traveling on the flight can assist, but they are not the authorities as far as diversions are concerned. Exceptional circumstances exist for active labor and uncontrolled bleeding, as well as ongoing CPR or the use of an AED. Doctors and flight attendants try to care for the patient outside these two conditions without a diversion. The most common reason for is inclement weather. Perhaps the winds at an airport are unsuitable for normal operations, or a thunderstorm exists over the approach path or the airport itself. Whatever the reason for the airport reverting to irregular operations, air traffic control will issue holding instructions to pilots. Holding allows pilots to do a few essential things. They can keep their planes up at an altitude and slow down, saving a lot of fuel. Additionally, pilots can start to loop their dispatcher into the unfolding situation. The dispatcher likely already knows that the plane has entered a hold before they hear from the pilots. When the pilots message, they send the fix they're holding at, their altitude, and fuel onboard. The dispatcher then runs this information through performance software to generate the anticipated fuel burn to the destination and the alternate. If no alternate was listed on the original release, they would dedicate one at this point. The pilots receive the dispatcher's new fuel calculations and use this to decide how long they can hold. The amount of time is figured by adding the anticipated fuel burn to the destination, then onward to the alternate if they don't make it in, and then the reserve fuel. The sum of these values is commonly called the "bingo" fuel number. If the pilots are still holding when the bingo figure is reached, they will leave the hold and head straight for their diversion airport. Pilots can hold for a longer time in hopes weather conditions will improve by changing their alternate. This can only be done with the dispatcher's approval as an amendment to their release. For example, a flight from
Los Angeles to Denver might have Casper, Wyoming as the alternate on the initial release. If they hold south of Denver while waiting for a storm to pass the airport, the dispatcher can make
Colorado Springs the new alternate if the weather is good there. The shorter distance between Colorado Springs and Denver compared to Casper would allow the pilots to wait 15-20 more minutes before heading to their alternate route. A line of thought that pilots process when a diversion is imminent is how many other planes will be heading to their alternate at the same time as them. It's a common practice to head to the alternate a few minutes before bingo fuel is reached, especially if pilots know that other flights have already started heading out of their holds to alternates. For example, 50 planes might divert when a . The nearby airports like Tulsa, Oklahoma City, Austin, and Houston have limits on how many diversions they can accept at a time. Pilots and dispatchers know this, so airlines do their best to spread diversions over these airports. Regional airlines will also use smaller fields like Lawton, OK, or Abilene, TX, where operations are established. Regardless of where pilots divert to, it's always best to be one of the first to divert rather than the last, especially if bingo fuel is fast approaching. Another issue that causes diversions is stronger headwinds than forecast. Pilots and dispatchers closely monitor the fuel situation as this kind of scenario unfolds. If it's a tight situation, terminal controllers can help pilots by putting their flight at the front of the arrivals line or giving them short vectors to final before pilots declare minimum fuel. Controllers understand the operational environment and would rather get the plane on the ground at its destination instead of diverting. Get all the latest here. A non-emergency diversion is required when a prospected landing at the alternate airport with the necessary reserve fuel is remotely in question. Pilots know they cannot land below the reserve fuel, and they determine their bingo fuel with this number as the guiding figure. A diversion is always to an airport that the dispatcher has approved and has added as an amendment to the flight plan. This ensures that the plane can be fueled at the alternate and continue to its destination. At the very worst, the airline has a company presence at the diversion airport to ensure passengers can get off the plane and make travel arrangements for the next day.