Some passengers described “total chaos” in the “systems failure” at Terminal 5, the Telegraph reports.
BA has apologised to passengers at the airport, saying there were “some issues” with its check-in system.
The problem has now been resolved.
A BA spokesman said: "Customers are being checked in as normal after an earlier problem was resolved. We are sorry for the temporary check-in problems which caused some delays for our customers first thing this morning.
"This issue is now resolved and our staff are working flat out to help customers get away on their holidays."
The delays come as holidaymakers are being warned they face lengthy delays at European airports due to tightened border checks.
