Allegations that a short-staffed Air India had diverted one flight's crew to another under "VIP pressure" prompted a dramatic passenger sit-in at Delhi airport last night, leading to both flights being delayed by at least seven hours.

A series of alleged crew rejigs, stemming from a Friday morning fog hold-up that ripped schedules, had consequences stretching till late this morning. A fully boarded Calcutta-bound flight was delayed 14 hours because there was no pilot, while its angry passengers defied an attempt to evict them from the plane.

Ironically, the protest against the "VIP culture" was led by an MP, Biju Janata Dal member Tathagata Satpathy, a passenger on the Delhi-Bhubaneswar flight whose crew were allegedly shifted to the Delhi-Bhopal flight.

Satpathy and another passenger, senior journalist Rajdeep Sardesai, alleged that two judges and a Madhya Pradesh minister had pressured Air India managing director Ashwani Lohani into switching crews.

Air India today denied having given "any preference to any particular flight".

"First, Air India announced the Bhopal flight had been cancelled. But just because there was a minister from Madhya Pradesh, they said the flight to Bhopal would go and not (the one to) Bhubaneswar," Satpathy told The Telegraph.

The Bhubaneswar flight (6.20pm) and Bhopal flight (7.30pm) had both been already rescheduled, to 9.30pm and 9.45pm respectively, when a 9pm announcement said the Bhopal flight had been cancelled. But 15 minutes later, Air India announced that the Bhopal flight was on and the Bhubaneswar flight stood cancelled.

As angry Bhubaneswar passengers sought an explanation, some ground officials apparently mentioned a crew switch. By then, some of the Bhopal-bound passengers, including the minister and the judges, had boarded their flight, sources said.

A furious Satpathy, joined by a group of fellow passengers, sat on a dharna at the boarding gate, blockading the rest of the Bhopal-bound fliers.

Sardesai, who didn't join the dharna, tweeted a running commentary. "One BJP min of state from MP and two judges on Bhopal flight. Is that reason enough for AI MD to ask pilots to move from one Flt to other?" he wrote.

His next tweet said: "Passengers on Bhubaneshwar flight say they will allow Bhopal flight to take off if judges who misused VVIP status come out."

He then tweeted: "It's close to 1am; neither Bhopal or Bhubaneshwar AI flights have left; dharna continues, this is India's national carrier!"

Air India sources said the airline eventually flew a crew from Bangalore into Delhi and operated the Bhubaneswar flight. Both flights left around 2.30am.

An amused Sardesai noted how the kerfuffle had left even the flight attendants confused, saying an airhostess welcomed the passengers to "Raja Bhoj airport in Bhopal" when the aircraft landed in Bhubaneswar.

Madhya Pradesh PWD minister Sartaj Singh denied having influenced Lohani, who had twice worked as managing director of Madhya Pradesh Tourism.

"It wasn't me who spoke to him," Sartaj told this newspaper. He, however, admitted talking to the "Air India management" to find out why his flight had been cancelled.

Sartaj said he had no idea if any judges were on board. He said an MP from Odisha had "politicised" the issue.

Maninder Singh, a Bhopal resident, echoed him: "There was a politician who did not want us to reach on time because his Bhubaneswar flight had been cancelled."

Air India sources said the crew assigned the Bhopal flight had completed their stipulated duty hours, which triggered the crisis. They said that Lohani, being a "hands-on" person, tried a rejig by requisitioning crew from Bangalore and elsewhere.

Earlier on Friday afternoon, a Delhi-bound flight was stalled mid-boarding in Bangalore for a lack of pilots as a fog-induced 4am-to-10am halt in take-offs in Delhi hit airline schedules and crew rosters countrywide. A witness said some passengers had boarded and the rest were held back by ground staff.

Later at night, passengers aboard AI022 from Delhi to Calcutta faced a similar situation. Scheduled for departure at 8.15pm, the passengers were allowed to board around midnight.

"We waited endlessly for the pilot. A couple of hours later, we were told to deplane," said Himadri Chatterjee, general manager (finance) with a Calcutta-based MNC.

"We were so agitated by then that we refused unless another flight was arranged. They came back with security personnel and said they could force us off the plane. Some of them even started to remove our cabin luggage."

But the passengers stood their ground. "It was harrowing. They ran out of milk and there was no water in the toilets. They could have at least put us up at a hotel instead of making us board if there was no pilot," he said.

"At 7.30am, airline staff told us they had arranged another flight at 9.30am. We were herded out through the international departure area to the domestic departure. The flight finally left at 10.30am."

Air India later tweeted: "Due to heavy fog since yesterday morning & resultant delays, most of the crew's duty time was limiting later on in the day. Crews were planned as per their arrivals from earlier flights, back to Delhi & sequenced based on the duty time remaining.

"At no time did AI give any preference to any particular flt. Arriving & available crews duty time remaining as per regulations was checked & were scheduled for the flts based on time & sequence."

The Indian Commercial Pilots Association too blamed the fog, denying that a pilot shortage had caused delays.

Its general secretary, Praveen Kirti, said it was possible, however, that not enough pilots trained in CAT III (a category of instrument landing) were available at the time. "Visibility was zero and not every AI pilot is CAT III-trained."