Flying between the neighbor islands is about to get more convenient.

Island Air, which is phasing in additional and larger aircraft, said Friday it plans to nearly double the number of interisland flights it offers by the beginning of May. The state’s second-largest carrier said it expects to offer up to 476 one-way flights each week between Oahu, Maui, Kauai and Hawaii island compared with the 266 flights per week it currently offers.

The announcement comes about six months after Hawaiian Airlines, with about 90 percent of the interisland market, said it would be adding two Boeing 717s to its fleet. One of those aircraft will enter service by the middle of this month, and the other one is scheduled to come online in March. Those two planes will boost the number of 128-seat 717s in Hawaiian’s fleet to 20.

Island Air said that over the next four months, Honolulu-Kahului round-trip flights will double to 16, Honolulu-Kona flights will increase to 10 from six and Honolulu-Lihue round-trip flights 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 by its newly leased Bombardier Q400 turboprops, which seat 78 passengers, are 30 percent faster than conventional turboprops and allow the airline to offer additional frequency because of the speed of the aircraft. The first Q400 began service Jan. 12. A second Q400 has been delivered and is being used for training. The airline plans to add up to seven new Q400s by the end of the year and put its existing fleet of five 64-seat ATR-72 aircraft out of service.

Island Air currently offers eight round trips daily between Honolulu and Kahului (one flight was added Wednesday), with three additional round trips on Fridays and Sundays. The airline also offers six round trips daily between Honolulu and Kona, with one additional round trip on Fridays and Sundays; and six round trips daily between Honolulu and Lihue.

Hawaiian’s jet service within the islands varies with more than 170 daily departures. For service on Hawaiian’s major interisland routes during the week of March 13-19, for example, Honolulu-Kahului has 27 to 29 daily round trips, Honolulu-Lihue has 17 to 20, Honolulu-Kona has 16 to 19 and Honolulu-Hilo has 13 to 16. Hawaiian also offers limited daily service between Kahului and Lihue, Kahului and Kona, Kahului and Hilo, and Lihue and Kona. During that particular week Hawaiian will offer 1,234 one-way flights.