JPMorgan has emerged as the latest brokerage firm to turn negative on a handful of airline stocks. (See also: Avoid Airline Stocks, Even at These Multiples: MS.)

In a research note examining the downtrodden sector reported on by Reuters, JPMorgan singled out industry juggernauts American Airlines (AAL

) and United Continental Holdings (UAL), together with budget carrier Spirit Airlines (SAVE), as the biggest victims of current industry dynamics. The analysts downgraded all three from “overweight” to “neutral” based on concerns that rising fuel costs and ongoing domestic pricing weakness could prevent them from hitting consensus estimates. Similar fears also led the brokerage to cut its target price on Delta Air Lines (DAL).

Analyst Jamie Baker and his colleagues noted that current consensus hints that fourth quarter Revenue per Available Seat Mile (RASM) metrics could be set to improve. They disagree with this assessment, arguing instead that…