A man reportedly boarded a British Airways flight at Heathrow after tailgating his way through security checks without a passport, ticket or boarding pass. 

The traveller, who has not been named, is said to have walked onto a BA flight to Oslo, Norway, on Saturday at 7.20am after avoiding checks at the departure gate.

Witness reported that cabin crew only noticed something was wrong because the flight was full and he kept sitting in passengers' assigned seats.

Police arrested the man, airport sources said, adding that he had passed through 'full security screening' before reaching the gate.

The traveller allegedly pretended to be with a family who passed through the final passport check at the gate before boarding the Airbus A320.

Mike LaCorte, who was aboard BA flight BA768 with his wife, saw the incident from his seat.

'This chap moved around until the plane filled up. And then a member of the cabin crew went over to speak to them. And it was clear that this person didn't have any boarding pass or anything at all,' he told The Telegraph. 

He described the traveller as a white man in his 'late twenties or early thirties, a scruffy solo traveller' wearing an 'off-white tracksuit' and carrying a 'small' rucksack.

Sources said the man had tailgated his way through automatic gates at the entrance to Terminal Three's security screening area.

After passing security, the man posed as a member of a family who had their passports and boarding passes inspected in the usual way.

Airport security, followed by armed police, arrived and removed the man from the plane.

'The cabin crew came in and tried to map where the seats were that he was sitting at, and then searched the cabin overhead bins,' the source added.

All genuine passengers then had to pass through security again. Sniffer dogs searched the airliner before the rightful passengers were allowed to board again, Mr LaCorte said.

'It was, like, three hours,' he said. 'How did he get on in the first place? It's the risk.'

Posting on X, one user wrote: 'Good grief, how can that happen in this day and age?'

Another wrote: 'Bloody impressive really. Not only tailgating security but also getting past the gate agents scanning boarding cards. They can spot hand luggage 5cm too big at five paces.'

One user replied in the thread: 'I imagine the gate guy/girl is getting a telling off about taking people's word for it when they claim they're with another group, but really you don't expect someone without a boarding pass even to be airside in the first place.'

The commenter responded: 'That was clearly their tactic, wasn't it. Slip through with a larger group that all marched up together. Can be done. 

'They check the faces of the passports shown, but may lose count of how many are waved on.' 

The Mail has contacted Heathrow Airport and BA for comment.