The Oahu Interscholastic Association and Interscholastic League of Honolulu have agreed to play a full slate of interleague, nonconference regular-season football games starting this fall.

The meaty part of what is a two-year pilot program has been worked out, with only minor details still being discussed, according to sources from both leagues who requested anonymity because the deal has not officially been announced.

Under the new format, all nine Open Division teams (six OIA and three ILH) will play a round-robin against each other to make eight games for each school. Only games within a team’s league, however, will count toward the two leagues’ standings. Interleague games would count only toward a team’s overall record.

For fans, a regular season full of games that pit Saint Louis, Kahuku, Mililani, Punahou, Waianae, Kamehameha, Farrington, Campbell and Kapolei against each other is sure to be a winning formula, and it will likely ensure large crowds and lucrative gate receipts.

Weekly enticing interleague matchups will also happen in Division I and D-II. The two ILH D-I teams (St. Francis and Damien) will go head to head with the eight in OIA D-I (Leilehua, Castle, Kailua, Moanalua, Aiea, Waipahu, Radford and Nanakuli) for a nine-game schedule. In D-II, the ILH’s ‘Iolani and Pac-Five will pencil in games against the OIA’s Kalani, Kaiser, Pearl City, Roosevelt, McKinley, Waialua, Kaimuki and Kalaheo.

The new plan is quite different than the so-called OIA-ILH alliance, which was shot down a few seasons ago, but one source believes this new format is far superior.

“This way, the two leagues will still have their own champions,” the source said. “It’s like in college, where you play teams in your conference and also schedule games against teams that are not in your conference.”

At the state-tournament level, there will be no changes to the formula. For example, the Open Division format of three OIA teams and one from the ILH will still be used. Both leagues are still planning to hold playoffs to determine league champions.

The historic agreement comes after a month of hard work and negotiation. In January, when the OIA decided it was changing its alignment from two divisions to three for 2018, it sought a way to fill the schedule for its six Open Division teams. Playing games against the ILH’s three Open squads — who have been lacking enough regular-season competition for years — was a natural fit and both leagues moved toward that end.

Sources said that cutting down on the frequent blowouts that have occurred in the past few seasons (with only two tiers in the regular season) and ensuring equitable and safe competition were the biggest reasons behind the new plan, which represents a major breakthrough for the two leagues. Except for a few seasons in the early 2000s, when the OIA and ILH scheduled a few early-season, interleague games for some of its schools, the two leagues have rarely competed on the field prior to the postseason since a rift in 1970 caused the public-school ILH teams to leave and join the OIA.

The interleague format is a big relief to the ILH, which has only seven teams (three in Open and four in D-I/II and no crossover games between the two divisions scheduled) that were stuck playing the same league opponents at least twice — and sometimes three or four times — per season.

From 1973 to 1998, the champions of the two leagues met in the Prep Bowl, which was the season finale and considered the de facto state championship. The state tournament, which started in 1999 and continues today, has always ended up with the champions of the OIA and ILH in the upper-division title game.

It’s unclear how the gate will be split. One early proposal from the negotiations calls for the OIA to receive 100 percent of proceeds after expenses from interleague games at OIA fields and 80 percent for interleague games at Aloha Stadium or ILH fields.

The leagues have yet to discuss radio or TV deals for interleague games.

Sources said one more step is necessary to finalize the deal — a vote by ILH school principals — but they said that it was a formality since the ILH ADs voted unanimously in favor of it. A few weeks ago, OIA principals gave the go-ahead for the OIA league office to schedule games how it saw fit (including against ILH teams), with the understanding that combining the two leagues into one was not a possibility.