Stansted Airport passengers complained of waiting more than two hours to receive their baggage in the early hours of Tuesday morning.
The problem emerged when around 30 delayed flights landed at the Essex airport between midnight and 3am amid poor visibility.
Oliver Williams, from London, described the airport as an "absolute shambles".
He said: "All staff have disappeared, hundreds of passengers awaiting baggage for hours and no water available."
Passengers were also frustrated by long queues at passport control.
Charley Allen, from Exeter, wrote on Twitter: "What's happening with passport control? 3am, thousands of people and all e-passport gates closed?"
An airport spokesman said all baggage was returned by around 4am and the airport has returned to normal operation.
Flights were delayed after air traffic controllers doubled the minimum distance between incoming aircraft due to fog.
A spokesman for Ryanair said: "Following earlier weather delays on flights arriving into London Stansted, a number of aircraft landed outside of scheduled operating hours, which resulted in some handling delays.
"We sincerely apologise to affected customers and have asked our handling agent at Stansted, Swissport, to take the necessary steps to ensure this does not recur."
An airport spokesman said: "Airlines and ground handling partners called in additional staff to help manage the situation and mitigate delays. Our own staff helped provide passengers with information and handed out water during the period.
"On behalf of our airlines, handling agents and the airport we apologise for the delays and inconvenience caused to passengers."
Stansted is the UK's fourth busiest airport, with 26 million passengers last year.