Beware that travel, usually ultra-compact like your Maclaren Atom stroller is, are made to be small. Overall, small wheels, small seat, and therefore, low weight and a small fold. Read more about the whole topic in this article about ultra-compact strollers and their pluses and downsides in this article.
Moving on, I would 100% recommend a bit larger, still lightweight stroller, but a mid-size one that only faces forward. Otherwise, you'll always struggle with a tall toddler in these. The smallest possible I am thinking of that could handle your little big one would be the Uppababy Minu for sure. Then, I am thinking about TFK Dot 2 (if available in your country), Baby Jogger City Mini2 or a Baby Jogger City Mini Zip, or, perhaps, a Mamas&Papas Armadillo. These will not be checked as cabin luggage, but they CAN be taken onboard as a part of free baby/child luggage. They'll simply take it from you when boarding, and give it back after you land and get off.
If, by chance, you still think about an ultracompact stroller, I'll suggest a Joolz Aer (or maybe an Ergobaby Metro+) as it has a taller backrest then most. Still, I myself would rather get a lightweight mid-size world-facing model to have my child napping comfortably.