By Alexander Cornwell and Tim Hepher

DOHA, June 22 (Reuters) - Two high-tech Airbus A350 jets sit idle with their windows taped and engines covered in a floodlit hangar in the Gulf, hobbled by an international legal dispute between European industrial giant Airbus and Qatar's national carrier.

From a distance, the planes might seem like any other long-haul jetliners crowding the busy Doha hub.

But a rare on-site visit by Reuters journalists showed what appeared to be evidence of damage to the surface of parts of the wings, tail and hull.

The two planes, worth around $300 million combined according to analysts, are among 23 grounded A350s at the centre of a $1 billion London court battle over whether the damage represents a potential safety risk, something Airbus strongly denies.

The planes were grounded by Qatar's regulator after premature paint erosion exposed damage to a metallic sub-layer that provides protection to the fuselage from lightning strikes.

Other airlines continue to fly the A350 after European regulators declared it safe, with several carriers recently acknowledging surface issues while calling them "cosmetic".

Reuters journalists were granted rare first-hand access after requesting the visit on the sidelines of an airline industry meeting in the Qatari capital, Doha, this week.

Sporadic surface flaws on the A350s viewed by Reuters included an elongated stretch of blistered and cracked or missing paint along the roof or crown of the jets.

In some areas including on the curved wingtips, the protective lightning mesh that sits between the hull and the paint appeared exposed and corroded.

In other parts it appeared to be missing, leaving areas of the composite hull exposed.

The paint on the tail of one of the A350s emblazoned with Qatar Airways' maroon Arabian Oryx emblem was pockmarked by cracked and missing paint that exposed the dull carbon beneath.

Reuters saw small areas of what appeared to be fraying or delaminated carbon threads on the hull and so-called 'rivet rash' or lost paint from fastener heads on the main wing areas.

Airbus and Qatar Airways had no immediate comment on Reuters' findings.

Shares in Airbus fell 2.4% on Wednesday amid weaker aerospace stocks.

EROSION

Airbus acknowledges quality flaws on the A350s, but denies they pose any safety risk because of the number of backup systems and tolerance built into the design.

Qatar Airways has argued this can't be known until further analysis, and is refusing to take more of the planes.

Airbus has argued that some paint erosion is a feature of the carbon-composite technology used to build all modern long-haul jets - a necessary trade-off for weight savings.

It says the cracks are caused by the way paint, anti-lightning material called ECF and the composite structure interact.

The tail does not all contain the ECF foil, prompting a debate over whether damage there comes from the same problem.

Qatar Airways has questioned Airbus' explanation, telling a UK court its similar Boeing 787s do not have the same problems.

A Reuters investigation last November revealed at least five other airlines had reported surface issues as far back as 2016, after the A350 entered service the previous year.

The European Union Aviation Safety Agency (EASA), which oversees the design of the jet, said the degradation seen in the surface protection "does not constitute an unsafe condition".

"EASA´s sole interest in this matter is aviation safety," a spokesperson said.

Qatar's own aviation regulator has declined to comment since the dispute began.

Amid hundreds of pages of conflicting technical court filings presented by both sides, Reuters has not been able to verify independently the cause of the damage.

Qatar Airways' Chief Executive Akbar Al Baker and Airbus Chief Executive Guillaume Faury had the opportunity to mingle during the three-day industry gathering in Qatar this week.

Asked whether the relationship had improved after the event, which included the two men seated next to each other over dinner, Al Baker suggested the two sides remain far apart.

"On a personal level I am friends with everyone but when it comes to an issue with my company, then it's a different story. If things were settled, we would not be still waiting for a trial to happen next year," he told a news conference.

Faury said this week he was in discussion with the airline and reported "progress in the sense that we are communicating".

One of the airline industry's most senior officials voiced concerns after the Doha meeting that the dispute could have a toxic effect on contractual ties across the industry.

"It would be much better if we were dealing with friends that than dealing in the courts," Willie Walsh, director general of the International Air Transport Association, told reporters.

(Reporting by Alexander Cornwell and Tim Hepher Editing by Mark Potter and Louise Heavens)