UPDATE 1-Greece's Aegean Airlines to join Star Alliance

* Aegean, Star Alliance teams to start integration work

* Star Alliance to number 26 carriers after process completed

(Adds official confirmation, comments)

ATHENS, May 26 (Reuters) - Greek carrier Aegean Airlines (AGNr.AT) will join the Star Alliance, which includes UAL Corp's United (UAUA.O), Germany's Lufthansa (LHAG.DE), Air Canada (ACa.TO) and Continental (CAL.N), it said on Tuesday.

The move would give Aegean, which became Greece's largest airline by passenger numbers last year, access to many markets across the globe with large communities of Greek descendants, executives said.

"Aegean is a welcome addition to the Star Alliance network, its home market is of strategic importance due to its geographic position in the eastern Mediterranean," Star Alliance CEO Jean Albrecht said in a statement.

Aegean, which competes with former state carrier Olympic Airlines, operates a fleet of 31 aircraft covering 47 domestic and international routes.

Members of the airline alliance cooperate on route scheduling and revenue sharing. The Star Alliance competes with two other alliances -- Sky Team and Oneworld.

"Becoming a member of Star Alliance represents both an honour and a great opportunity," said Aegean Chairman Theodore Vassilakis. "As we continue to grow our network we are committed to become valuable contributors to this great alliance."

Executives said teams from Aegean and Star Alliance will start the integration work shortly, expecting completion in about 12 months. Once complete, the Star Alliance will encompass a total of 26 carriers.

Aegean shares have gained 20.3 percent since the start of the year, underperforming the broader Greek market's .ATG 27.5 percent advance. They trade 8 times estimated earnings compared to a multiple of 24 for Lufthansa, according to Reuters Estimates data. (Reporting by George Georgiopoulos; editing by Simon Jessop)