Island Air, which is phasing additional and larger aircraft into its fleet, plans to nearly double the number of interisland flights it offers by the beginning of May.

The state’s second-largest carrier said today it expects to offer up to 476 one-way flights each week between Oahu, Maui, Kauai and Hawaii island compared to the 266 flights per week it currently offers.

Island Air said over the next four months that Honolulu-Kahului round-trip flights will double to 16, Honolulu-Kona flights will increase to 10 from six and the number of round-trip flights between Honolulu and Lihue will grow to eight from six. The airline also said it will add flights to accommodate high travel days (Fridays, Saturdays, Sundays and Mondays) and spring-break travel demands.

“The added flight service is in response to growing demand from our customers and travel partners and also reflects the improved operational efficiencies of the new Q400 aircraft that are being phased into our fleet,” David Uchiyama, president and CEO of Island Air, said in a statement.

Island Air’s expansion is being fueled its newly leased Bombardier Q400 turboprops, which seat 78 passengers, are 30 percent faster than conventional turboprops and allow Island Air to offer additional frequency because of the speed of the aircraft. The first Q400 began service on Jan. 12. The airline plans to add up to seven new Q400s by the end of the year and transition its existing fleet of five 64-seat ATR-72 aircraft out of service.