An AirBaltic flight carrying 109 holidaymakers was grounded on Saturday after four of the five crew members failed alcohol tests.

According to the Norwegian newspaper Dagbladet , police were tipped off prior to departure by a passenger who suspected the crew had been drinking.

Police carried out checks and discovered both the captain and first officer, as well as two of the three flight attendants, were over the drink-fly limit.

The four were taken into custody, while the charter flight from Oslo to Crete, operated by the Latvian budget carrier AirBaltic on behalf of the travel firm Star Tour, was delayed for around five hours until sober crew members had been located.

Passengers were initially told the pilot was “unwell”, Dagbladet reports.

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Janis Vanagds, an AirBaltic spokesman, told the Latvian English-language website LSM that it has a “zero tolerance policy”.

"Zero tolerance means no alcohol," Vanags said, "It's very straightforward - safety is our number one priority.

"There has been an initial test and that is being followed up with more detailed tests. When we have the results we will take appropriate action. I apologize to all customers who have been affected by this incident.”

Helena Therese Langeland, a passenger on board, said: "It is surprising that people who have such huge responsibility in their jobs, don’t take it seriously and have so little professionalism.”

AirBaltic, Latvia’s flag carrier, was founded in 1995 and serves 60 destinations including London and Aberdeen.

The drink-fly limit is extremely stringent. In the UK it is 20 milligrammes of alcohol per 100ml of blood, compared to the drink-drive limit of 80mg per 100ml.

Test failures are rare. According to a 2010 report, the Federal Aviation Administration – the US equivalent of the CAA – more than 10,000 pilots are tested each year, with about 12 failing, on average.