DALLAS -- Most restrictions on flights between the U.S. and Mexico will lift on Sunday, a change expected to bring more options and possibly lower prices for travellers.

American, Delta and Southwest have already announced that they will offer new flights across the border later this year. A spokesman for United says that airline is watching the demand for flights and will respond accordingly.

The United States and Mexico agreed in December to open their aviation markets to each other's carriers. Rules that had generally limited two or three airlines from each country to a particular route will go away.

Airlines on both sides of the border will be able to fly whatever routes they want as often as they want and set their own prices.