By Rajesh Kumar Singh and Tim Hepher

NEW DELHI (Reuters) -Airline bosses are tentatively voicing greater confidence in Boeing's ability to deliver jets at the right quality in a step towards ending years of reputational damage for the embattled planemaker.

An annual summit of airline leaders in New Delhi this week struck a more optimistic tone about Boeing's recovery from overlapping safety, regulatory and industrial crises, though executives stressed Boeing still had much work left to do.

"What we've seen quarter to quarter is an improvement in safety, an improvement in quality," Seattle-based Alaska Airlines CEO Ben Minicucci told Reuters at the International Air Transport Association's annual meeting.

"Are they yet there? No, there's still a lot of work."

In January last year, a door missing four bolts blew off a new Alaska Airlines Boeing 737 MAX jet at 16,000 feet. The ripple effect from the incident caused a crisis throughout the aviation industry, hitting suppliers, carriers and passengers.

Planemakers often have to run the gauntlet of airline criticism at IATA's annual meeting, where IATA head Willie Walsh last year urged Boeing to learn from errors that fuelled a crisis beginning with fatal crashes of two MAX jets in 2018 and 2019.

One of Boeing's most vocal recent critics has been Tim Clark, president of Emirates, the largest customer for big jets like the Boeing 777 and its long-delayed successor the 777X.

At his annual sit-down with reporters at the summit this year, Clark spoke more positively about getting "clearer messages" from Boeing's recently appointed leadership.

He welcomed a change of style under CEO Kelly Ortberg, revealing he had never met Ortberg's ousted predecessor Dave Calhoun.

"It was nice to meet the head of Boeing," he said.

Clark, whose airline has 205 of the still uncertified 777X on order, suggested growing confidence from Boeing in private.

"When I talk about cautious optimism, in the last few years I had seen none of that" he said.

Ortberg, who took the helm last August, has said he will address safety and quality concerns and repair trust with regulators, staff and customers.

Boeing customers said the measures are showing some results.

While Boeing is still trying to ramp up production, there have been improvements in quality and visibility of deliveries.

"There is still further to go but it is definitely an improving story," said Peter Barrett, CEO of lessor SMBC Aviation, a major leasing company and Boeing customer.