Neither CanJet nor WestJet would have a free aircraft to charter under such situations, since they operate very close to the bone on aircraft utilization, and finding a charter on a few hours notice is "saving" a scheduled carrier such as AF. As for the fare, and Concorde loads, both are much lower than suggested by others here. BA has been discounting Concorde since it returned to the skies, and it can be had for about the same as Business, and certainly less than First. AF has always charged less than BA, and always offered second seats free in Amex promos in low season, which this is. On my BA Concorde flight, going over on a peak day, there were still 20-30 open seats [just 100 in total], and returning on a quiet day, less than half the plane was filled, and only 10 of us in the back cabin, including Michael Jackson's entourage of 3, plus a couple of Mickey Mouse dolls.