Diet company NutriSystem Inc. will replace Frontier Airlines Holdings Inc. on the S&P SmallCap 600 on Tuesday, Standard & Poor's said Friday.
Frontier filed for bankruptcy on Friday, the fourth carrier to do so over the past few weeks.
Horsham, Pa.-based NutriSystem's shares rose $1.19, or 5.7 percent, to $19.25 in after-hours trading. The stock closed down 88 cents, or 4.6 percent, at $18.21.