A computer failure affecting airport baggage systems may force some passengers to fly without their luggage.
Heathrow and Gatwick are among the airports that have experienced problems, though Gatwick has said that the issue has now been resolved, with no lost baggage or delayed flights.
A BA spokesman said: "We are doing all we can to minimise disruption caused by an IT failure which is affecting the performance of baggage systems at numerous airports.
"We are very sorry if customers have not received their baggage and we will reunite them as quickly as possible."
A spokesman for management at Heathrow Airport said: "We are aware that there is a European issue with the Sita system that manages bags for some airlines.
"We understand that Sita is applying a fix to the problem and we hope that it will be resolved soon. In the meantime airlines that are affected are processing bags manually. The problem is causing some delays but is not currently causing any flight cancellations at Heathrow."