How airlines spoil fuel in order to keep pilots off their payroll
Flights must be manned with 2 pilots. However, longer intercontinental flights must be manned with 3 or 4 pilots, because legal work and rest times regulations require pilots to have inflight-rest periods.
Many of such flights are just beyond these regulatory limits. Due to the low price for fuel, airlines prefer to fly these flights with maximum speed instead of employing another copilot.
5% to 10%, 3-15 tons, more fuel is regularly burned for such purposes. This practice is frequently used and increases fuel consumption per flight significantly. The lower the costs for fuel, the more likely, an airline will prefer to fly fuel-spoiling fast.