JetBlue Airways Corp. and Spirit Airlines Inc. said late Friday that they have appealed a court ruling that earlier this week blocked their planned merger. JetBlue JBLU, -1.19% and Spirit SAVE, +17.19% announced the appeal in a terse press release that provided no more details, adding only that the process is “consistent with the requirements of the merger agreement.” Wall Street was split on whether the airlines would be legally obliged to appeal the Tuesday ruling, which sided with the Justice Department ...