[H1][FONT size=4]Alliance among 3 airlines approved[/FONT][/H1]WASHINGTON (AP) -- The government on Friday approved an alliance between Delta, Northwest and Continental airlines that will allow them to sell seats on each others' flights if they agree to rules aimed at keeping air travel competitive. [BR][BR]Low-fare airlines lobbied against the deal, calling it a virtual merger among the third-, fourth- and fifth-largest U.S. carriers. Eight state attorneys general also opposed the agreement because they said it could stifle competition, raise prices and hurt service. [BR][BR]The agreement, called a code-sharing alliance, allows the airlines to offer more destinations without flying more planes and offer reciprocal perks such as frequent flier miles. [BR][BR]The proposed rules also limit the number of flights the airlines may share and forbid the airlines from agreeing on fares, capacity or changes in routes. They also require the airlines to give up leases on some airport gates which are used less than six times a day. [BR][BR]Regulators, struggling with the decision, delayed the ruling four times since the carriers applied for their approval on August 23. It was approved conditionally on Friday by the transportation and justice departments. [BR][BR]Major airlines, which have lost billions of dollars since the September 11 terrorist attacks in New York and Washington, are looking for ways to better compete with the low-fare airlines. [BR][BR]A code-sharing deal approved in October allowed bankrupt airlines United Airlines and US Airways to share passengers on 192 daily flights.