The CAA has set out what it has described as "clear expectations" of airlines in an open letter to the aviation sector amid worries jet fuel supply constraints could yet disrupt flight schedules this summer, urging carriers put passengers' needs first.

Its warning came hours before Jet2 reiterated it was confident of operating its flying programme as normal over the coming months despite the war in Iran. "Our message to holidaymakers is that summer is on," said Chief Executive Steve Heapy.

Addressing the aviation industry, the CAA's Head of Consumer Protection Anna Bowles acknowledged she was writing to carriers "at a challenging time" and insisted she recognised "the significant disruption" the sector was facing owing to the conflict in the Middle East, highlighting airspace restrictions, fuel supply constraints and the impact of the crisis on consumer confidence.

"The situation has created significant uncertainties, which are subject to change at short notice, and presents complex challenges for airlines to manage," said Bowles.

However, she added: "With this in mind, we are writing to set clear expectations, including how passengers are supported when services are disrupted, especially where flights are cancelled.

"While we recognise the efforts many airlines are making in demanding circumstances, this letter is intended to remind industry of its existing obligations and encourage continued focus on passenger needs during this period."

Bowles warned airlines they should not be selling flights "where there is a reasonable expectation those flights will not operate", adding that where flight cancellations are "unavoidable", passengers should be notified in "timely" fashion via clear, prompt communications.

Bowles also reiterated passengers are entitled to fixed-sum compensation in the event they receive less than 14 days' notice of a cancellation, save for in the case of "extraordinary circumstances".

"While appreciating the rising price of jet fuel creates significant operational challenges for airlines, the view of the CAA is that decisions by airlines to cancel flights or consolidate schedules for operational or commercial reasons (including fuel prices) would not constitute extraordinary circumstances," Bowles stressed.

Extraordinary circumstances, she said, could include a fuel shortage at an airport preventing a flight from departing. However, she added where there are multiple considerations involved in a decision to cancel a flight, a ruling on whether those circumstances are extraordinary would depend on the specific facts and would be assessed on a case-by-case basis.

On fuel surcharges, Bowles reminded carriers they must present the full and final cost of a booking upfront, including any mandatory jet fuel charges.

"All applicable taxes, charges, surcharges and fees must also be clearly itemised," she said. "Mandatory charges must not be presented incrementally or misrepresented at any stage of the booking process. We therefore consider price increases to existing flight-only bookings are not permissible."

With regards to package holiday bookings, Bowles said price increases are permitted "in limited circumstances" under the Package Travel Regulations.

"However, where consumers are offered a 'price promise' at the time of booking that the price of their package will not increase, we expect terms and conditions to reflect this and consider that price increases under PTR Regulation 10 would not be permissible," Bowles added.

"Where these rules are breached, consumers may have rights to refunds, cancellation or other redress."