According to literally the first thing I found on the Internet, the airlines take in about 1% of the world's GDP which doesn't sound like a great deal when they

According to literally the first thing I found on the Internet, the airlines take in about 1% of the world's GDP which doesn't sound like a great deal when they emit twice that much in CO2. However, I'm guessing the businesses they support that wouldn't exist otherwise easily make up the difference. I'd guess ~10% of the GDP (most international tourism, shipping, business meetings).