Bristol Airport has apologised after passengers faced "unacceptable" security queues - with one family claiming to have been left £1,600 out of pocket after they missed their flight due to the delays.
Customers described arriving at the airport on Friday morning to find people queueing out of the building, with further "chaos" inside.
Some missed their flights, while others were able to travel only due to airlines taking off later.
Kieron Sheridan said his family faced "absolute carnage" after arriving for their Ryanair flight to Valencia.
They joined the queue outside the terminal at 4.45am, with their flight due to take off at 6.35am.
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He tweeted: "Absolute carnage at Bristol airport due to poor security organisation and lack of personnel.
"Queued for nearly 2 hours and only got half way through the queue when advised our flight had gone without us.
"The queue started outside of the building, we joined it at 4.45am. We were still at least 45 mins away from getting through security when we had to give up."
Mr Sheridan added: "Having travelled abroad on average four times a year for the last 30 years, I have never seen anything like it.
"Despite doing everything in our power to get off on a family holiday, we feel absolutely robbed of that opportunity, and £1,600 out of pocket."
Mr Sheridan said he had contacted the airport and was waiting for a reply.
Max Walsh, a reporter for ITV News West Country, described the scenes at the airport as "absolute carnage".
He tweeted: "Trying to catch a flight to Belfast. I've been queueing for 90 mins and still nowhere near security.
"Queueing system has completely broken down as barriers are pushed over and hundreds of people face missing flights.
"Saw one person having a panic attack in the queue. Security cannot cope.
"I've just made it to the plane which is only half full and was supposed to take off at 7am. Expect to be delayed until most passengers make it through."
In a statement, Bristol Airport said the issue was due to fewer security staff working than expected.
A spokeswoman confirmed at 9.20am that queues had "returned to normal".
She said: "The security queues in the early morning were unacceptable and we apologise to all customers who were impacted.
"Far fewer security staff were working than planned. We're urgently discussing the issue with our security business partner so passengers receive the service levels they rightly expect.
"The queues at security have now returned to normal. Our advice for passengers flying later today is unchanged - we recommend you arrive at least two hours ahead of your scheduled time of departure."
