A British Airways flight descended into "pandemonium" when passengers and cabin crew after hazmat-suit-clad firefighters stormed the aircraft.
Melanie Wells flew out for the £7,500 all-inclusive, luxury TUI package holiday of eight days in Egypt alongside her 19-year-old daughter Imogen on December 23.
However, after boarding the flight at London Gatwick Airport, the 61-year-old developed a bad headache, which she initially put down to the "extreme temperature" on the plane.
Within two hours of taking off, Ms Wells said passengers and crew members had fallen "seriously ill", with members of staff collapsing down the aisle.
After an emergency landing in Venice, the plane was swarmed by emergency workers in hazmat suits with testing devices.
Terrified she felt ill due to breathing some kind of "toxic fumes", Ms Wells described the plane as "pandemonium" before being diverted back to London after an eight-hour delay.
Ms Wells insists the experience "ruined" the start of their holiday, and is calling for more compensation than the £2,000 she claims the airline has already offered.
British Airways confirmed the plane was diverted due to a "technical issue" on board.
Hazmat crews boarded the plane once it touched down in Italy
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The plane was forced to land at Venice Airport
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She said: "I'd really pushed the boat out. I hadn't been very well so treated me and my daughter to an ultra-high-end all-inclusive in Sharm El Sheikh. I hadn't been away for ages, it was definitely much-needed.
"When we boarded, the temperature was so extreme that I started to feel unwell. It was supersonically hot. I ended up getting a really bad headache and put it down to the heat.
"About an hour and a half in the air, crew members suddenly began running down the aisle backwards and forwards. I didn't know what was going on.
"There was one mum whose eyes rolled into the back of her head. The crew looking after them had actually collapsed because of the fumes."
Melanie Wells
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Ms Wells, from Eastbourne, East Sussex, said: "About six people fell seriously ill on board while we were in the air. I felt very unwell.
"I felt nauseous and had a headache. At the time I put it down to stress but now looking back I think it was fumes."
After an eight-hour wait in Italy, the plane was diverted back to London Gatwick before landing in Egypt the following morning.
On arrival home, Melanie submitted a complaint to BA who she says have offered £2,130 in compensation for the cancelled flight, meal expenses and issues faced.
Passengers were taken off the flight
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But Melanie says the airline are refusing to refund her for the first night of accommodation they missed in Egypt due to the delays.
Melanie said: "We were travelling for 40 hours. We were utterly exhausted. The experience was horrific. It was definitely a flight from hell.
"BA have performed in the most cavalier manner. The distress and trauma we went through, it was utterly traumatic. It ruined the start of our holiday.
"I want the £500 for the missed accommodation too. It was a horrific experience."
Emergency crews at the scene in Venice Airport
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A British Airways spokesman said: "The safety of our customers and colleagues is always our top priority and our aircraft diverted as a precaution because of a technical issue.
"We've apologised to our customers for their experience and have offered compensation accordingly."
They also said there was no evidence of any fumes on board and the plane was checked and back in service the next day but failed to clarify what the 'technical issue' was.