It's one thing to be told your flight is delayed. It's another to be told your flight is cancelled.
But passengers are now dealing with an even more baffling phenomenon: discovering their flight doesn't even exist.
They're paying for tickets, getting confirmation of their bookings and in some cases even checking in online pre-flight — but when they turn up at the airport, they're told their flight is no such thing.
Passenger Erin Levi made the unexpected discovery last month when she arrived at Newark Airport in New Jersey for her flight to Paris.
She'd booked her $270 one-way ticket with Level, a low-cost airline owned by the International Airlines Group.
Hours before the September 9 flight, Ms Levi, 35, checked in on the airline's website.
But at Newark Airport, she tried, and failed, to find her gate. She also couldn't find the carrier's service desk.
It was then she found out even though the airline accepted her money and confirmed her booking, it hadn't even launched its Newark to Paris route yet.
The flight didn't exist.
"I've travelled to over 40 countries — even on a handwritten ticket to Uzbekistan — and this has never happened before," Ms Levi told ABC News.
What Ms Levi didn't find out until too late, was that weeks before the flight, Level decided to delay the launch of its Newark-Paris service until September 18 — nine days after Ms Levi's scheduled flight — due to operational reasons, but hadn't notified passengers or posted the update on its website, according to ABC News.
Ms Levi had to find another way to get to Paris, where she was attending a wedding, and Level apologised to passengers.
"Indeed, on August 20, we took the prudent decision to postpone by two weeks the launch of our operations between Paris and New York, planned for September 4, for operational reasons," Level told ABC News.
"Customers impacted by this launch delay have been alerted by email, sent to (the) address registered in their booking (or to the travel agency that did the booking).
"We sincerely apologise for the inconvenience caused and delay to our passengers' travel plans," it said, adding it would fully refund tickets.
Weirdly, that wasn't an isolated incident.
In August, a British family was left stranded when they arrived at the airport to find their flight with low-budget carrier Primera Air — which has just filed for bankruptcy — also didn't exist.
Nicki Bryce and her family were to fly from Birmingham, UK to Toronto on August 3, having paid more than $5900 for their tickets months earlier, The Telegraph reported.
But when they got to the check-in desk, they were told the Danish carrier's Birmingham-Toronto service had never actually launched.
Ms Bryce said not only had she not been told Primera had scrapped the launch of the service months earlier, she had actually been able to update the booking to include her newborn son a week before the flight date.
"Not once did (Primera) flag up that the service had been cancelled, and they still took the money for my son to get onto a flight that didn't exist," she told the Telegraph, saying the devastated family lost money in hotel and travel expenses as a result.
Other passengers have taken to social media and review sites to report they had been similarly stung.
In some cases passengers booked with the airline directly, while others booked through third-party platforms.
The phenomenon also recently stumped travel expert JT Genter from The Points Guy.
In November, the frequent flyer and his partner were due to fly business class from Belgrade to Berlin with Air Serbia, having booked tickets months earlier using Etihad points.
The night before, when they were checking in online, a pop-up message said there was an issue with their tickets. But they were advised to see someone at the airport before their flight, and their flight status was listed as "confirmed".
"Having not received any contact from Etihad or Air Serbia, we assumed all was well with the flight and ticket," Mr Genter said.
"We arrived at the airport especially early … but when we tried to check in at the business class line, we got a cold response from the agent that there were no Berlin flights today. We were directed over to the ticket counter.
"Long story short: Air Serbia had reduced its schedule and cancelled our flight months earlier, but had neglected to tell us."
Mr Genter said he learnt valuable lessons from the experience. Among them: Confirm your flight with an outside source.
"Crazily enough, Air Serbia continued to show our flight as confirmed, even though the flight schedule was supposedly changed months ago," he said.
"I guess that a new step that I need to add to my pre-flight checklist is to check a week out with an independent source such as ExpertFlyer that the flight still exists."
He also suggested passengers call the airline if an error message or issue arose pre-flight, and take photos of everything.
"This wasn't necessary this time around, but I've learned from past similar situations to take photos of any documents you receive," he said.
But would travel insurance help in these cases?
Travel insurance expert Natalie Ball, director of Comparetravelinsurance.com.au, said the same rules applied to cancelled flights whether passengers found out that day, or weeks earlier — it depended on the reason for the cancellation.
"In a nutshell, travel delays or cancellations where the airline is at fault are not covered, whereas unforeseen disruptions outside the airlines' control are usually claimable events," she told news.com.au.
"Your travel insurance will typically cover for missed or delayed flights due to severe weather conditions, airport system outages, strikes, if you're unfit to fly or if you have an accident on the way to the airport. Travel insurance is unlikely to cover for cancellations due to an airline's mechanical fault, overbooking aircraft or passenger's tardiness in getting themselves to the airport on time."