Go! airlines and Island Air have reached a tentative code-sharing agreement for flights between Kahului and Hilo and Kahului and Lihue.

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

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

Go! currently has a code-share agreement with Mokulele, dubbed go!Express, for flights serving smaller interisland routes such as Kona and Kahului, Kahului and Kapalua, and Kapalua and Honolulu.

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

Go! and Island Air could launch the new Kahului to Hilo and Kahului to Lihue code-shares in the next several weeks, pending the 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.

Go!, a discount carrier, launched its interisland service in June 2006.

Island Air, founded in 1980 as Princeville Airways, is a niche player that serves smaller destinations such as Kapalua, Moloka'i and Lana'i.

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