The European plane maker has confirmed that the cracks have been found in various parts of the wing rib attachments of five superjumbos – one belonging to Qantas, two to Singapore Airlines, one to Emirates and one of Airbus's development aircraft.

Less than a centimetre in length, the cracks were found on the L-shaped feet of the wing ribs. The feet attach the rib – a vertical fixture – to the cover of the wing.

Airbus engineers discovered the problem during $130 million worth of repair work to Qantas's first A380, which has been at Singapore's Changi Airport since November 2010 after a mid-air engine explosion.

Airbus's head of engineering, Charles Champion, told Fairfax Media that its analysis had determined that the tiny cracks posed no threat to the safety of the aircraft.

"The aircraft is absolutely safe because there are so many ways for the loads to travel within the structure of the wing," he said.

"As it really is not a safety issue, we will inspect them over time ... within the next four years – some of them before."

The inspection of the wing ribs will take place when each aircraft is due for heavy maintenance.

The aircraft manufacturer has traced the problem to an aluminium material used in the wing ribs – called 7449 – which tends to be more sensitive to the way the parts are assembled on the wing.

Airbus had ruled out as a cause of the cracks flight loads, fatigue or the large size of the aircraft.

"It is nothing to do actually with the loads. We found it is very random. We actually found them on ribs across the wing and from one aircraft to another it can be a different rib foot," Mr Champion said.

"On some aircraft we found almost none and on others we found several across the wing on both sides."

Airbus has been in informing air-safety authorities, including the European Aviation Safety Agency, of the cracks but there are no plans to issue airworthiness directives requiring airlines to take action.

"We are not deciding on our own that all of this is a non-event. All of this analysis is shared and demonstrated and challenged by the ... authorities," Mr Champion said. "Based on the analysis, the aircraft is safe. We will take the opportunity of the double c-check to introduce repairs."

Qantas confirmed yesterday that "minuscule cracking" was found in the wing-rib attachments of the Nancy-Bird Walton under repair in Singapore.

“No immediate action is required by A380 operators because the cracking presents no risk whatsoever to flight safety," a spokesman said.

“Formal guidance is being developed by Airbus that is likely to require A380 operators to inspect wing ribs for this type of cracking every four years – in line with scheduled maintenance checks. Qantas will comply fully with this guidance when it is published.”

Singapore Airlines also confirmed today that a "small number of cracks" had been found on the wing-rib feet of a second of its A380s during inspections in the second half of last year.

"These pose no safety issue and repairs were carried out on the [first] aircraft. Repairs were subsequently carried out on a second aircraft," a spokesman said.

"We have kept the relevant regulatory authorities fully informed, and are carrying out inspections and any necessary repairs on other A380s as they go in for C-checks."

The cracks in the wing ribs of Qantas's A380 in Singapore have since been fixed, but other repair work to get the aircraft back into service is not expected to be finished until March.

Qantas has a further 11 superjumbos in its fleet which fly long-haul international routes to London and Los Angeles. It will take delivery of a further two A380s next year but has deferred orders for a further six superjumbos by up to six years.

Mr Champion's comments were made late last night, shortly after Fairfax Media first published the story about the discovery of the cracks.