The airline said the hold ups, which affected passengers due to fly on Sunday, were caused by an upgrade to its check-in system.
This Morning presenter Phillip Schofield was among those affected.
He ended up returning home after missing their flight – but not before he had tweeted his followers about what was happening, with one tweet telling BA: "You are s***."
Another tweet said: "Not a single British Airways person here to explain," adding: "If you’re flying British Airways from Terminal 5 this evening. You’d better come early!"
Heathrow swiftly replied, saying: "@Schofe Hi Phillip, we regret that you’ve been affected by the system issues. All parties are currently working on resolving this."
BA reports the problems have been resolved and flights are operating normally.
