Flybe passengers on a new "flagship" route were left with a six hour coach journey when their aircraft was grounded.
The 18:40 service from Newquay to Heathrow could not take-off on Sunday because of a "technical issue".
Cornwall Airport Newquay said passengers were offered "rebooking for another flight or ground transport to London Heathrow".
One passenger said "words fail me" with another calling it a "a PR disaster".
Chris Dennis from London was one of those meant to be on board who was transferred to a coach.
He said: "We got to Heathrow around 03:00 and bed and 04:00. I'm very tired today as had to be at work at 08:30.
"It's a bit of a PR disaster considering it's the first day of the flagship new route from Heathrow to Newquay. I think they need more investment in the planes.
"Flybe staff were good but I'm left wondering why an alternative plane did not come and get us."
The new service replaces a link with London Gatwick and will operate four flights a day.
It is being officially launched on Monday, with the airport saying: "Today we're celebrating our first flights between @HeathrowAirport and @Newquay_Airport taking off!"
Today we're celebrating our first flights between @HeathrowAirport and @Newquay_Airport taking off! Passengers on board will be greeted with this message in Cornish.— Flybe ✈ (@flybe) April 1, 2019
Do we have any Cornish speakers here? pic.twitter.com/DnzmBxlD0T
Another passenger said she has missed a day of work in London because of the cancellation and has been been put on the next available flight, on Monday afternoon.
"All a bit of a shambles as a customer experience", she added.
In a statement, Cornwall Airport Newquay confirmed the flight was cancelled "due to an aircraft technical issue".
"This was the only London Heathrow flight affected and they are running to schedule today", it added.