Haw. Rev. Stat. § 39-19

If at any time the director of finance, with the approval of the governor, shall issue general obligation bonds for the purpose of refunding aviation revenue bonds, then so long as any general obligation refunding bonds are outstanding, the State covenants with the holders of the bonds that it will levy and collect an aviation fuel tax in an amount at least sufficient to provide for the payment of the principal and interest thereof, which amounts are hereby pledged to the payment of that principal and interest. The State reserves the right to issue subsequent bonds, whether general obligation or revenue bonds, equally secured by a pledge of the revenues of the aviation fuel tax.