The MailOnline has conducted a report to discover the reason why.
It cites examples like a non-stop flight from New York to Houston, Texas taking around three hours and 50 minutes today, whereas in 1973 the same flight took only two hours and 37 minutes.
Other examples are less drastic, a flight between London and Edinburgh taking around 10 minutes longer today than it did in the mid-'90s.
The reason? Going slower saves money.
It seems that airlines instruct pilots to maintain a lower average speed in order to save fuel, one of the most significant operating costs. It seems that even shaving a few miles per hour off average speeds can result in significant savings across the year.
For example, Northwest Airlines in the US claims to have saved 162 gallons of fuel on a 2008 Paris to Minneapolis flight by cutting its average speed from 542mph to 532mph. This saved the airline nearly £300, and added only eight minutes onto the journey.
Northwest reckons it has saved £300,000 on its LA to Hawaii route in one year, simply by slowing down a little.
Southwest, another US airline, estimates a saving of £21million after adding one-to-three minutes to every flight.
The report also cites congestion, both on the ground and in the sky, as a reason for journey times increasing, as the sheer number of flights operating at any one time leads to delays and fewer opportunities for improved flight paths.
It is also noted that although some individual flights may be getting lengthier, there are now far more options for non-stop flights than there were in the 1970s. Routes that may have taken days due to multiple stops, such as journeys to Southeast Asia, are now reachable with a single flight.
Have you noticed journey times getting longer?