Well airlines have been trying many things to save the cost.
I posted just a portion of the full article, as no one would have read it then, it was 3 times longer. 
Most flyers were comfortable with added times, and no one even noticed the longer flights, which within US only added 3 to 4 minutes anyway. Most airliners are doing it already, and it is done for the benefit of the passengers.
If they don't slow down, they will have to add extra to fuel surcharges on the ticket (some of it is already there). Which one will you take, pay $50 to $100 dollar more, or arrive 5 to 10 minutes later. In this case, you don't have a choice, LoL, you go by what they airliners will do, and what is acceptable to most passengers, and most passengers will care to save the money than to arrive 5 minutes later on their destination.
Other factors involved. The winds are also a very important factor. If the airplane is facing strong headwinds, it will slow down the aircraft anyway, and it will have to struggle more to move forward. Contrarily, if the airplane is assisted by Tailwinds, it will actually push the airplane faster and help save the fuel.
This is where flight routing comes into play, as also indicated in the article above, reference to $20 million software that projects the best routes, to save the fuel. They airliners chose the best routes that have less head winds. But on the Long Flights like the flights from London to New York, the Tailwinds are present in One Direction only.
Due to global winds pattern, the winds move from West to East, so the flights from New York to London are faster than from London to New York. This can also be observed while traveling to Pakistan from USA. Flight back home to Pakistan is always a little faster, sometimes as much as 20 to 30 minutes or even more than comming back.
Happy slow flying ....
