Travelers bound for San Francisco were stranded this morning, after a teeny tiny stowaway caused their flight to be canceled.

It all went down on British Airways flight 285, which was scheduled to take off from Heathrow for SFO at 10:40 a.m. GMT (that's 2:40 a.m. PT). According to The Telegraph, passengers, who had already boarded the plane, were told they had to disembark after an unticketed mouse was discovered onboard.

The BBC reports that passengers were informed that a "rather unusual occurrence" meant that they all had to leave the flight, as "planes cannot take off with mice on board."

(It's apparently not that unusual, though, at least in England? As the Daily Mail reports, in 2015 a flight from Birmingham to Dubai that contained "Ex-boxing champ David Haye" was delayed after a similar issue.)

Passengers were asked to leave the plane and board a new one, but faced a four-hour delay as "it would be several hours before a gate would be available for the new plane," the Telegraph reports. According to CBS 5, they finally finally took off at 2:56 p.m. local time, for a rodent-free landing expected at 1:10 p.m. PT in SF.

"We know almost everyone wants to fly with us to San Francisco," British Airways said by emailed statement, "but on this occasion there was one very small customer who we had to send back to the gate. Everyone with two legs is now on their way to California, and we are sorry for the delay."