Standard & Poor’s Ratings Services lowered its ratings on AirTran Holdings Inc., parent of AirTran Airways, saying heavy losses are expected because of high and volatile fuel prices.

The downgrade of AirTran’s corporate credit rating to CCC+ from B- reflects the losses and resulting pressure on the company’s liquidity, according to a written statement from Standard & Poor’s credit analyst Betsy Snyder. AirTran, which is based in Orlando, has its largest hub in Atlanta.

According to Standard & Poor’s, AirTran’s liquidity is adequate for the near term and losses could total over $100 million this year, with the potential for losses in 2009 as well.

Standard & Poor’s also removed AirTran ratings from CreditWatch and said the outlook is stable.

AirTran spokesman Tad Hutcheson said from AirTran’s perspective, the downgrade was “based on the sour economy and the high fuel prices.”

Standard & Poor’s also affirmed its B corporate credit rating for Atlanta-based Delta Air Lines and removed its ratings on Delta from CreditWatch. Its rating outlook is negative.

The ratings service said it expects Delta will post “a significant loss” of close to $500 million this year before non-cash charges, due to high and volatile fuel costs. “But it’s financial performance should continue to be better than those of most peer large U.S. airlines,” according to Standard & Poor’s credit analyst Philip Baggaley.