NEW YORK ( TheStreet) -- The airline sector has made heavy advances in afternoon trading, on the heels of Morgan Stanley ( MS ) touting the sector's attractiveness. The Amex Airline index has gone up by 3.5% to $29.50. "Now that ... previously exuberant expectations have normalized as evidenced by price action in the last one to two months versus improving trends and ... the risk of a liquidity squeeze at a major carrier in 2010 has fallen; we believe investors will become increasingly willing to bet on the cycle," wrote Morgan Stanley analyst William J. Greene in a note to investors cited by the Wall Street Journal. Greene has boosted his outlook for the sector to attractive from in-line. On top of that, he also lifted his ratings on AMR ( AMR) and UAL ( UAUA) to overweight from equalweight and lowered his ratings on Alaska Air ( ALK) to underweight from equalweight.