New research suggests that air travel in tropics increases global warming more than a flight in temperate latitudes.
As well as producing carbon dioxide and contrails, planes also produce nitrogen oxide, which triggers both the creation of the warming gas ozone, and the destruction of another greenhouse gas, methane, according to the study.
According to Keith Shine of the University of Reading, UK, in mid-latitudes, the ozone and methane reactions cancel each other out and you get zero net warming from nitrogen oxide emissions, reports New Scientist.
But the brighter sunlight in the tropics is very efficient at converting nitrogen oxide to ozone - in fact it creates ozone five times faster than in the air of mid-latitudes, according to Shine's calculations.
Whereas methane destruction only increases marginally, Shine added.
Worryingly, the warming effects of ozone are particularly strong at a plane's typical cruising altitude of 35,000 feet, he adds.
The research raises the question of whether future attempts to control aircraft emissions should consider extra penalties for flights in tropical countries where air travel is booming. India, for instance, has the fastest growing airline fleet in the world.
The study is published in the Journal of Geophysical Research.