Some airlines allegedly reduce fares on certain routes to a level at which they lose money, in order to drive competitors off those routes  However, this method of eliminating competition cannot be profitable in the long run
Once an airline successfully implements this method, any attempt to recoup the earlier losses by charging high fares on that route for an extended period would only provide competitors with a better opportunity to undercut the airline' s fares
When airlines dramatically reduce their fares on a particular route, the total number of air passengers on that route increases greatly.