Airline stocks were knocked lower Friday, with the sector on track to suffer the biggest one-day loss in nearly 3 years, as the recent drop in oil prices and concerns over a slowing economy acted as a one-two punch for the group. The NYSE Arca Airline Index slid 5.1% toward a fourth-straight decline. Friday’s loss was headed for the biggest one-day loss since Feb. 26, 2016. Crude futures surged 2.4% Friday, as OPEC and its allies reached a deal to cut production, but has declined 22% over the past three months. Lower oil prices lowers fuel costs for air carriers, but it also leads to undisciplined capacity growth that could hurt unit revenue performance. Analyst Hunter Keay at Wolfe Research downgraded the airline sector, saying that while a recession and lower oil are both “toxic” for air carriers, “we trust airlines to react better to a recession that we trust them NOT to behave poorly with lower oil prices.” Among the sector’s more active components, shares of American Airlines Group Inc. plunged 9.1%, Delta Air Lines Inc. dropped 4.3%, JetBlue Airways Corp. tumbled 5.8% Southwest Airlines Co. lost 4.1% and United Continental Holdings Inc. shed 5.4%. The airline index has lost 6.0% over the past three months, while the Dow Jones Industrial Average has declined 5.8%.