The British Airways Notifier has uncovered a practice across the industry that deliberately places weight on flights, increasing greenhouse gas emissions. higher rates for refueling at their destination airports.
This may mean additional annual emissions equivalent to those in a major city.
The BA said that it was customary to carry additional fuel for "operational, safety and cost reasons". [1
Cost savings for one flight can be as little as just over £ 10 – though savings can go up to hundreds of pounds.
Researchers have calculated that every fifth of all European flights includes some element of a fuel tank. .
The practice of European routes may lead to additional annual greenhouse gas emissions. equivalent to that produced by a city of 100,000 people.
Critics argue that the widespread use of the practice undermines the aviation industry's claim that it is committed to reducing its carbon footprint.
John Sauven, CEO of Greenpeace UK, told the BBC it was a "classic example of a company making profits before the planet".
He added: "Therefore, we cannot afford another decade to believe in corporate washing and wait for voluntary carbon reductions.
" We need strict regulations to limit aviation emissions, because while there is money for pollution, they will pollute as much as they can. "
International Airlines Group (IAG), the company that owns BA, says it wants to be the world's leading sustainability aviation group.
BA prides itself on even printing its flight magazine on lighter paper to save weight.  However, the BBC Panorama saw dozens of BA internal documents showing that up to six tonnes of extra fuel had been loaded on planes in this manner.
Airlines can save money on the fact that the price of aviation fuel varies between European destinations.
BA internal staff say the company – like many airlines operating short routes in Europe – has computer software that calculates whether costs can be saved by refueling.
The software will calculate whether cost savings are to be made. If available, crews are refueling.
An example of documents seen by Panorama shows that a recent BA flight to Italy produced nearly three tonnes of additional fuel.
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The cost savings of this trip were less than £ 40, but documents that Panorama saw showed that it could be even lower than that.
IAG generated annual profits of 2.9 billion euros (2.6 billion pounds) in 2018, about 80 percent of which came from BA.
BA's inner man described the practice as "hypocritical".
"For such a large company to try to save so little while emitting so much extra CO2 seems unjustified in the current climate," he said
BA said it was common practice for airlines to carry extra fuel for some flights.
The airline told BA that this was mainly for short-haul destinations "where there are significant differences in prices between European airports".
He stated that the additional emissions from the airline are approximately two per cent of the total additional emissions generated by all airlines that tank fuel in Europe, based on Eurocontrol studies.
BA indicated that since 2012, all flights in Europe have been covered by the EU Emissions Trading Scheme.  He added that from 2020 the company would offset all CO2 emissions from its domestic flights to the UK.
Eurocontrol, the authority that coordinates air traffic control for Europe, estimates that tanking in Europe results in the burning of 286,000 tonnes of additional fuel each year and the release of an additional 901,000 tonnes of carbon dioxide.
It is estimated that the practice saves airlines a total of € 265 million (£ 228 million) annually.  Eurocontrol described the practice as "dubious" at a time when aviation is being challenged for its contribution to climate change.
But the BA syndicator stated: "I have long been a BA employee.
"I'm very proud to be a part of BA, but it honestly makes me sad and frustrated."
Panorama: Can flying turn green? is on BBC1 at 20:30 GMT on 11 November.