Continental Airlines is bringing back its Mileathon promotion and Continental OnePass members can earn up to 100,000 bonus miles for completing credit-earning activities at continental.com from April 1 through June 30, 2010. The Mileathon promotion will be the same as last year, except the duration is only three months compared to the four months members had to accrue credits last year.

For each qualifying activity completed, you will receive credits, which will translate into bonus miles at the end of the promotion. Qualifying activity will include booking flights online, staying at partner hotels, renting cars and more. The top credit-earners will also receive a Grand Reward, a cruise package to your choice of destinations that includes first or business class airfare and a $500 gift card.

Only members residing in the 48 contiguous U.S. are eligible for the promotion and registration begins April 1 and ends May 31, 2010 at continental.com/mileathon. Credit accrual begins on the date you register.