Flight delays are usually caused by bad weather, staff strikes or technical problems with aircraft.
But sometimes the animal kingdom can also throw a spanner in the works, often birds.
But other creatures have been known to cause havoc, too – from turtles to moose – by getting themselves onto the runway.
An alligator at Orlando International Airport held up a Spirit Airlines flight
Cloven traffic is common in Alaska – some 800 moose live in greater Anchorage alone. Here’s one on a road near the city’s airport
However, at Orlando International it’s alligators that officials have to watch out for, because around 230 of them live in the airport’s 13,000 acres of water.
Workers at the hub are always on the lookout to keep the reptiles away from the airfield, but can’t always control the predators.
Earlier this year, a gator’s appearance alarmed passengers as it was seen lumbering across the tarmac toward a pond.
A Spirit Airlines flight had to wait about five minutes before it could taxi to the gate.
One of the passengers onboard says an airport truck arrived at the pond to make sure the alligator didn’t return to the taxiway.
At JFK Airport in New York, staff have to be extra cautious during diamondback terrapins’ nesting season. Last year almost 40 of the critters were rounded up after wandering too close to the runway
A box full of terrapins that were scooped up after venturing dangerously close to the runway at JFK Airport
Elsewhere in the US, the waters around two New York airports have brought unwanted vistors that the Port Authority have had to remove.
At JFK airport, staff have to be extra cautious during nesting season for diamondback terrapins.
Last July almost 40 of the critters were rounded up after wandering too close to the runway and released to safer areas.
The Port Authority had installed plastic tubing to act as a barrier, leading to a nearly 50 per cent drop in turtles on the airfield.
Flippin’ heck: Traffic had to be delayed at Utqiagvik airport in Alaska’s northernmost city after a seal lolled on the runway
But it was later discovered that the barriers are underwater during high tide – rendering them useless.
Meanwhile at La Guardia Airport in New York, the Army Corps of Engineers had to be called in January 2017 when a 15ft dead whale washed up near the end of a runway.
And in Utqiagvik, Alaska’s northernmost city, airport authorities were faced with a huge seal, blocking any attempt at takeoffs.
Traffic had to be delayed while animal control came in to remove it in October last year.
While elsewhere in Alaska biologists and wildlife technicians are often brought in to airports to wrangle musk ox, caribou and moose that wander on to the airfield.
And for Jackson Hole Airport, located inside Grand Teton National Park in Wyoming, moose and elk hanging around the hub are a frequent site.
Two wild hares bounce along Linate airport runway in Milan as they try to evade capture from handlers
At Milan’s Linate Airport, volunteers are employed to visit the airport grounds to blow whistles and wave to deter hares from affecting operations.
The animals first played havoc with the radar systems at the Italian airport in June 2007 and have been known to wander on to the airfield on occasion ever since.
At Manchester Airport, wildlife officers have to be on hand to keep sneaky foxes away from the aircraft.
In 2012, one had a very near miss with a Boeing 757 cargo plane after it ran into the path of the jet as it hurtled down the runway.
A fox had a very near miss with a Boeing 757 cargo plane at Manchester Airport in 2012 after it ran into the path of the jet as it hurtled down the runway
Wildlife officers at Manchester Airport say they have to be on hand to keep sneaky foxes away from the aircraft
While earlier this year, another one of the creatures was seen darting across a runway before being chased by security – which caused operations to momentarily stop.
And in remote airports in Australia, keeping kangaroos away from the runway can prove a hard task.
Recently a flight carrying nearly three dozen passengers had to be cancelled after hitting a stray kangaroo while preparing for take off at Mildura airport in south-eastern Australia.
The Rex Airlines plane was in the initial stages of take-off, in the state of Victoria, when the bizarre collision occurred in darkness.
A spokeswoman for the regional carrier, based in New Mascot, New South Wales, said the kangaroo was struck by the plane’s right propeller.