SEATTLE, May 21 /PRNewswire-FirstCall/ -- With the Memorial Day holiday comes the beginning of the summer travel season. Alaska Airlines and Horizon Air offer the following tips for stress-free travel. More information is available in the 'Know Before You Go' section of the airlines' Web sites -- alaskaair.com and horizonair.com.

1. Be prepared for security procedures. The Transportation Security Administration (TSA) has specific rules for carrying liquids and gels in carry-on luggage, in addition to procedures related to electronics. Become familiar with all their procedures, as well as prohibited items, by checking the TSA Web site, www.tsa.gov.
2. Be aware of passport requirements for international travel. Passengers traveling between the United States, Canada and Mexico are required to have a passport. For more information, visit the U.S. Department of State Web site at www.travel.state.gov.
3. Know when to arrive at the airport and gate. Passengers should arrive at the airport at least two hours before a domestic departure and three hours before an international flight. Travelers should contact individual airports for specific recommended arrival times. Alaska and Horizon customers must be at the gate at least 30 minutes before a domestic departure and 40 minutes before an international flight. These guidelines apply to all airports, regardless of size.
4. Allow extra time to get to the airport. Parking lots may be full during peak travel periods. Alaska and Horizon encourage passengers to take alternative transportation to the airport or park at a nearby satellite parking lot.
5. Check in online. Alaska and Horizon passengers can check in online up to 24 hours before a domestic or international flight at alaskaair.com or horizonair.com. International passengers can enter passport information online. Passengers who check in online should leave ample time to check any luggage at the airport. Alaska Airlines Mileage Plan members earn 1,000 Mileage Plan miles the first time they check in online.
6. Use a check-in kiosk. Alaska and Horizon provide more than 400 convenient check-in kiosks at airports and many off-site locations. Kiosks allow passengers to check in for flights, print boarding passes, pay to check additional pieces of luggage, and change seat assignments.