United Airlines said Friday it will start requiring minimum stays for nearly all domestic flights beginning in October. It is also raising its cheapest fares by as much as $90 one-way.

The second-largest U.S. carrier said the moves are among a number of changes it is making to combat record high fuel prices. The Chicago-based airline has been among the most aggressive in the industry in pushing fares and fuel surcharges higher in recent months, and its latest policy could prompt other carriers to consider following suit.

Starting Oct. 6, most United fares will require a one- to three-night or weekend-night minimum stay, spokeswoman Robin Urbanski said.

The new rules, which apply to nearly every ticket, are bound to be unpopular with business travelers who prefer to catch a flight out early in the morning so they can make it back home in time for dinner.

Major carriers scrapped most minimum-stay rules — put in place largely to discourage big-budget corporate travelers from snatching up the cheapest seats — years ago, although a number of airlines have been tightening up restrictions and tacking on fees in recent months as the price of fuel has soared.

United and US Airways last week joined American Airlines in charging passengers $15 to check their first piece of luggage.

How long passengers have to stay under United's new minimum-stay policy will depend on the destinations involved, the price of the ticket and the length of the flight.

For example, travelers booking the cheapest seats between Chicago and Minneapolis or Boston and San Diego will now be forced to stay three nights or the entire weekend, Urbanski said.

United also has raised its lowest fares by $1 to $90 one-way, meaning the least expensive available United ticket will now cost travelers $69 to $199 one-way, depending on the length of the flight.

For example, the cheapest one-way ticket for the 770-mile flight from Denver to St. Louis now costs $99, up from $89 before. A bargain ticket for a longer flight like Austin, Texas, to Los Angeles — a journey of nearly 1,240 miles — now costs $139, up from $79 one-way, Urbanski said.