The exchange traded fund that tracks airliner companies has taken off as summer revelers fill seats and lower fuel prices provide relief for the industry.

Guggenheim Airline (NYSEArca: FAA) gained 6.7% over the past month and is up 19.8% year-to-date.

According to a press release, U.S. airlines posted a profit of $518 million in the first quarter.

Southwest Airlines (NYSE: LUV) reported that June 2012 load factor, or the measure of average occupancy on airlines, was 84.4%, compared to 83.9% for the same month year-over-year. Additionally, passenger revenue per ASM is projected to increase 6% in June year-over-year.

The lower oil prices are cutting down airline costs. WTI crude was trading at $89.6 per barrel Wednesday. [ETFs for Lower Oil Prices]

Additionally, airliners are adding new routes to boost air traffic. For instance, Southwest is adding up to four daily nonstop filghts and JetBlue (NasdaqGS: JBLU) plans on serving Grand Cayman, according to a press release.

Looking ahead, JetBlue will release its earnings on July 25.