Cramer: Buy Southwest Airlines: TheStreet's founder continues to be bullish on the aviation stock, as the company reported a record load factor for May.

TheStreet's founder Jim Cramer on Friday reiterated his bullish stance on Southwest Airlines.

"I urge people to buy Southwest," Cramer told TheStreet's Rhonda Schaffler, adding, "I think American Airlines is good."

As for JetBlue Airways, the company "has not been the one that I like, but it's case by case now with airlines," Cramer said.

In April, Cramer called Southwest the "single best" airline stock out there, and later that month, after Southwest reported first-quarter results that topped analysts' expectations, Cramer said he likes what Southwest is doing, noting that the company "never lost money during the down cycle."

In afternoon trading on Friday, shares of Southwest were changing hands at $43.67, down 1.2%; JetBlue shares were trading at $18.12, down 1.7%; and American Airlines shares were trading at $33.04, down 1.1%.

Cramer's latest comments on airline stocks came after JetBlue on Friday reported that capacity growth outpaced traffic in May and cut its capacity growth outlook for 2016.

The Long Island City, N.Y., airline said May traffic increased by 10.7% from a year ago, while capacity went up by 12.1%. Load factor for the month was down to 84.6% from 85.7% in May 2015.

Revenue per available seat mile, or RASM, dropped by 7% in May, and JetBlue anticipated that RASM would decline between 7.5% and 8.5% in the second quarter.

For the full year, JetBlue lowered its capacity growth forecast to between 8% and 9.5% from 8.5% to 10.5%.

For its part, Southwest Airlines on Wednesday reported a 6.4% year-over-year increase in May traffic on a 4.6% rise in capacity. Load factor of 85.8% was a record for May, bringing the load factor to 82.2% for the first five months of the year.

The Dallas airline carrier continues to estimate modest growth in operating revenue per available seat mile for the 2016 second quarter, based on May's results and positive trends in June.

Meanwhile, American Airlines on Thursday reported that May traffic grew 0.5% year over year, while capacity increased 1.7%. Domestic traffic rose 1.4% on 1.2% capacity growth, while international traffic fell 1.4% on a 0.5% increase in capacity. Total passenger load factor fell 0.9 percentage points to 81.9%.

The Fort Worth airline continues to anticipate a 6% to 8% decline in consolidated passenger revenue per available seat mile for the 2016 second quarter.

(Armie lee - TheStreet)