Adams, who often speaks out about veganism, likes to eat a diet full of whole foods.
This lunch was no different, featuring a simple avocado, garnished with a squeeze of lemon and Mexican spice.
'Delicious vegan lunch'
"What am I eating you ask?" Adams wrote on Instagram. "It's only the best food on the planet that I brought with me for the plane ride. I was 36k over Indonesia when I had this.
"If you swipe over to the next photo you'll see a close-up. Avocado with fresh lemon and a Mexican spice that I love called Tajin. No bread. I only discovered this spice in the past year. Totally delicious vegan lunch."
Vegan for years
Adams, who has been vegan for many years, doesn't shy away from promoting the benefits of a plant-based diet.
Among many pro-vegan Instagram posts, one he shared in 2017 said: "I stopped eating animals including fish when I was 28 and I've never looked back. You can get all the protein you need from plants.
"It's great to see the change that is happening as people embrace a more plant-based diet, but we still have a long way to go. If you want to see your health improve and you care about the planet, go vegan.
"PS: you can't be a true environmentalist if you eat animals."