Island Air and go! airlines have reached a tentative code-sharing agreement for flights between Kahului and Hilo, and between Kahului and Lihu'e.

Mesa Air Group, the Phoenix-based parent of go!, said it hopes to expand the code-sharing agreement with Island Air once a separate code-sharing pact with Mokulele Airlines expires April 28.

"This tentative agreement will allow go! to extend its network and offer the people of Hawai'i an even greater choice for interisland travel," said Mesa CEO Jonathan Ornstein.

The go! code-share agreement with Mokulele, dubbed go!Express, covers flights serving smaller interisland routes — such as between Kona and Kahului, Kahului and Kapalua, and Kapalua and Honolulu.

But that service, launched in April 2007, has been on the rocks since November, when Mokulele partnered with Republic Airways to compete head-on with go! in its main interisland routes.

Island Air and go! could launch the new Kahului to Hilo and Kahului to Lihu'e code-shares in the next several weeks, pending on completion of a definitive agreement.

An expansion that would include the go!Express routes will likely occur after April ,once the Mokulele deal expires, according to a Mesa spokesman.

"Going forward, we expect this agreement with go! will provide new opportunities to grow our business here in the Islands," said Island Air's chairman, Charles Willis.