BBC:
For the last fortnight, as drones and missiles have whistled through the skies above Iran and the Gulf, air traffic controllers have been shepherding passenger jets through safer but congested airspace on the edge of the war.
A glance at a flight tracker map shows how busy Egypt and Georgia have become.
Working side-by-side, each controller looks after a different section of the map, co-ordinating with colleagues which planes are entering and leaving their airspace.
On a normal day an individual controller might manage six aircraft in their area at a time. But when there’s a war on, it could be double that.
“The brain can only give that amount of concentration at that level of intensity for 20-30 minutes,” says retired air traffic controller, Brian Roche.
He spent 18 years in the job, first for the Royal Air Force in various countries and then for passenger jets in London where he was part of a unit tasked with handling emergency distress calls.
During busy periods, more controllers are brought in to manage the greater volume of aircraft in particular areas and controllers are rotated more frequently to ensure they don’t become overwhelmed.
Usually shifts would be 45-60 minutes long with 20-30 minutes off, says Roche. But during times of conflict they will likely only do a 20-minute stint and then break for the same length of time.
“The controllers at the moment are working unbelievable shifts, [dealing with] unbelievable amounts of traffic,” he says.
The downing of a Malaysia Airlines MH17 flight in 2014 by a Russian-made missile in eastern Ukraine, which killed all 298 people on board, highlights how conflict can impact the route of passenger planes.
At the time, Ukraine was a relatively low-level conflict zone, but fighting had recently expanded into the air and in the preceding months a number of military planes had been shot down. It is also a scenario no-one wants repeated.
Last week, six American crew members were killed after their refuelling aircraft crashed in western Iraq.
The tanker had been involved in ongoing US operations against Iran and was one of two aircraft involved in the incident. The second landed safely. The US Central Command confirmed it was not the result of hostile or friendly fire.
When airspace is suddenly shut or congested, controllers communicate with pilots about where they need to go, how much fuel they have and which airports can accommodate their type of aircraft.
Controllers must also ensure all planes, which come in an array of sizes, are safely separated both vertically and horizontally because large passenger jets cause greater turbulence and instability for the aircraft around them.
That means smaller jets need to be guided away and given more of a buffer, while a tiny business jet might need to relocate altogether.
