Passengers at Heathrow Airport were facing long queues on Sunday as the Easter holidays got under way.
The airport blamed the disruption on Covid checks required by destination countries and “high passenger volumes”.
But there were also reports of staff shortages and problems with the e-gate passport checkpoints, as travellers took to social media to air their frustrations.
Some said they had waited hours to check in and take off as the airport confirmed “congestion” was affecting Terminal 2.
Other travellers said several automatic e-gates – which are staffed by Border Force – used to process passengers, were not operating properly.
The Home Office has been contacted for comment.
One passenger reported having sat on a plane for two hours waiting for take-off and said the reason given was staff shortage issues.
The travel chaos comes at the start of the Easter break, with an increase in holidaymakers understood to be driving up passenger numbers.
A Heathrow spokesperson said: “Due to high passenger volumes and the Covid documentation checks still required by many end destinations, Terminal 2 departures has experienced some congestion today.
“Our teams are supporting our airline partners to get passengers away on their journeys as quickly as possible and we apologise for any inconvenience this has caused.”