Just as some American drivers are making a run for the border to get cheaper Mexican gas in Tijuana, airlines have to scrimp and save where they can. They've been retiring less fuel-efficient jets (and reducing service), and even cleaning their planes more often, since even that little bit helps.
Airlines also comparison-shop at the "pump." A spokesperson for the Washington-based carrier Horizon Air was quoted in the Montreal Gazette as saying: "We'll top off, take more fuel than we really need from an airport that has the cheapest fuel, and not buy fuel at the more expensive airports."
And like those suburban granddads who never go faster than 55 down the highway, airlines are asking their pilots go a bit slower. Airlines such as JetBlue and the always price-conscious Southwest have been doing this for a while—in JetBlue's case, since 2006. But with fuel showing no signs of getting cheaper, it's safe to say the practice is only going to get more common.
In most cases, the slightly longer flight times are hardly noticeable. For instance, a Northwest flight from Paris to Minneapolis in May was lengthened by eight minutes, to eight hours and 59 minutes. The change in speed, from 532 mph rather than 542, saved the airline about $535 dollars—and 162 gallons of fuel.
Sometimes airlines have lengthened their published flight times to account for such slowdowns. Other times, however, the extra time may be simply absorbed into the extra flight time already built into the schedule for traffic delays or taxing. But if all that extra time is being eaten into, are flight delays likely to get more common than they already are? I guess we'll find out soon enough.