One world alliance is an alliance with similar ideas and ideals of Star-Alliance only with different members. One world was formed in 1998 by American Airlines, British Airways, Cathay Pacific, and Qantas. There are now four new members which are Iberia, Finnair, Aer Lingus, and Lan Chile*. They serve over 550 destinations in more than 130 countries. They have the same ideals as Star-Alliance such as that you have priority standby, baggage limits, baggage handling and lounge access to other airlines lounges. For example if you are on a flight on Aer Lingus from Dublin to Chicago, and you are a Emerald or Saphire member of oneworld or are in First or Buisness class on the flight you can have access to American's Admirals Club. Check out One World on the web at www.oneworldalliance.com
*Note: Canadian Airlines was a former member of One World but was purchased by Star-Alliance member Air Canada so all Canadian flights are opperated by Air Canada and mileage may be used on any Star-Alliance member.