It is taking longer and longer to fly from A to B. Or so airline schedules would have you believe.

Despite advances in technology and efficiency in the aviation industry, the time allowed on the schedule for planes to reach their destination is growing, according to a new study, and some say airlines are doing it deliberately to ensure they are always on-time, a practise known as "schedule padding".

The accusation is that airlines are coming under increasing pressure to have as high an on-time performance score (OTP) as possible, and are consequently allowing themselves plenty of wiggle room when allotting flight times.

Take, for example, the short hop from London Heathrow to Edinburgh. In 1996 every flight heading north was allotted a block time of 75 minutes or less. However, by 2015, the majority of airlines now expect to take 85 minutes.

The graph below shows the gradual increase in block time for the 330-mile flight.

The flight block times from London to Edinburgh since 1996

Other routes have shown the same trend.

The block times for Madrid to Berlin since 1996

The block flight times between Gatwick and Chicago O'Hare

The block flight times between Tokyo and Fukuoka since 1996

The report by aviation analysts OAG uses data to "draw attention to the fact that some airlines schedule longer to fly between two points than others. This may be considered as 'schedule padding'."

The observation is certainly not new.

In 2013, an AirTran Airways pilot told Reader's Digest that "airlines really have adjusted their flight arrival times so they can have a better record of on-time arrivals, so they might say a flight takes two hours when it really takes an hour and 45 minutes".

In the same year, Jim Paton, senior lecturer in the Department of Air Transport at Cranfield University, told the BBC: "The practice of buffering the airline schedule times is something that is very common, almost universal in Europe and in other parts of the world."

What Is On-time Peformance?

If you arrange to meet your friend at 3:00 p.m. and they arrive at 10 past, you would say they are late. If your plane is scheduled to arrive at its destination at 3:00 p.m. and it arrives at 10 past, it is on time.

This is according to the industry standard method of measuring punctuality.

Flightstats.com, an aviation monitoring website that runs an annual OTP awards, accept 15 minutes within scheduled arrival as on-time. A spokesperson for EasyJet told Telegraph Travel that the arrival time is taken from when the parking brake is applied - that is when you arrive at your gate. Incidentally, the departure time is taken from when the aircraft wheels begin to move (faster than three knots, roughly 3.5mph).

Media outlets, such as Telegraph Travel, are likely to run stories on how punctual airlines are so it's increasingly a key performance indicator and a way of marketing an airline's strength to the public.

The Civil Aviation Authority (CAA) also publishes information on how good airlines are at time-keeping, using 15 minutes as its late benchmark.

Why Are Flight Times Getting Longer?

"It's not as simple as assuming airlines have increased block times to reduce the risk of being late," said John Grant, a senior analyst at OAG.

The OAG report highlights a number of factors, while Grant says the airlines are not "devious" in attempting to spruce up their OTP, but are instead responding to different pressures.

"For one thing, different aircraft fly at different speeds," the report says, citing how a British Airways flight from London Heathrow to Chicago O'Hare will have a block time of 8hrs 55min, while an American Airlines flight has 9hrs 55mins.

The time it takes to taxi from the runway to the gate also needs to be accounted for - Amsterdam's new Polderbaan runway is cited as an example as it was built 15 minutes taxi from the terminal.

Congestion at either origin or destination also needs to be taken into consideration, with airports operating at or close to capacity requiring airlines to expect delays. For example, the report says BA were so struck by delays at Heathrow last summer on some routes to the US that it took the decision to "drop some frequencies... to give more breathing space and improve OTP". BA denies this is the case.

And finally, as with anyone's schedule, if you pack it too full and something goes wrong, the ripple effect will mess up the entire day. So airlines act conservatively.

Do Airlines Pad Their Schedule to Improve Their OTP?

They say no.

A spokesperson for BA said: "We regularly review our flight plans and timings to ensure that we can meet our published departure and arrival times and customers can plan their journeys accordingly. The weather, type of aircraft, air traffic control restrictions, airport infrastructure and geopolitical considerations will all play a part in the decisions we take about whether to increase or decrease each route's published flight time in our schedule."

A spokesperson for EasyJet told Telgraph Travel: "We work out scheduled flight times using three year averages to arrive at an accurate number.

"We invest a lot of time to get this right. Our business model is based on high asset utilisation which means using our aircraft as efficiently as possible is key to give our passengers and crew certainty."

Ryanair, which claims one of the highest OTPs in the industry, said: "At the end of each season all scheduled flight times are adjusted up or down to reflect the average flight times recorded on each route over that season. We do not and have never adjusted flight times to improve on-time performance, as this would reduce the efficiency of our operations."

Does It Matter?

Yes and no.

Unless you happen to be on the flight that never leaves on time.

The report says it comes down to managing expectations. If you arrive ten minutes early on a flight that was scheduled 10 minutes shorter ten years ago you're still going to be happy. However, 10 minutes late on a short scheduled flight time and you'll be miffed. So, in that sense airlines are shifting the schedules to protect your experience and their repuation.

We asked John Grant from OAG what makes one airline better at being on-time than another.

"Very little, to be honest," he said. "Airlines that operate to very large airports with lots of departures a day obviously have more challenges to face with the sheer volumes of movements at the airports which can show themselves as longer waiting times to taxi, waiting for a gate to become available for the plane to offload passengers from etc. But airlines that operate to such airports allow for that in their planning and daily operation, working hard with airports and suppliers to make sure the whole operation runs as smoothly as possible for all airlines."

So, no excuse really.