EasyJet has issued an apology to 29 passengers after a flight from Malaga to Bristol left the airport without them.
Flight EZY6056 departed from the Spanish city on Saturday with the group still waiting in the airport due to "an issue at the boarding gate".
All hold luggage had already been loaded on to the aircraft in time for the 9.15pm departure from Malaga, leaving passengers stranded with just their hand luggage.
A spokeswoman for the airline said 19 customers were placed on the next available flight to Gatwick at 10.30pm and the remaining 10 stayed overnight in Malaga before flying to Bristol the next day.
"EasyJet is in the process of contacting and apologising to the 29 passengers who did not board their flight from Malaga to Bristol on Saturday 5 October due to an issue at the boarding gate," the spokeswoman said.
"We have launched an investigation to understand what happened and will be offering flight vouchers and a refund of onward travel arrangements from Gatwick as a gesture of goodwill to the affected passengers.
"EasyJet arranged for 19 passengers to travel on the next available service to Gatwick and arranged accommodation for 10 passengers who travelled to Bristol the next day."
The spokeswoman said the passengers' luggage and boarding passes had both been scanned before the group proceeded to the walkway.
A total of 110 passengers were able to board the plane but it is believed a second barrier then did not open for the remaining 29.
The group queued in the corridor behind the second barrier - where they stood and watched their plane take off without them.
Iain Locke, 58, of Pensford in Somerset, told the Bristol Post the group were trapped in the corridor for 20 minutes.
Mr Locke told the paper: "I turned round to the guy beside me and said 'I don't want to alarm you, but the plane has gone'. I just couldn't believe it.
"I've flown a lot and I know there are measures in place for the pilot and crew to check the correct number of passengers are on the aircraft.
"I find it unbelievable that a flight could take off with passengers missing."
The luggage was flown to Bristol Airport, where it was reunited with the passengers after their flights home, the easyJet spokeswoman said.
Additional reporting by Press Association