Air transport operates within the earths atmosphere. Extreme wx events are showing a dramatic increase over the last twenty to thirty years. There could well come a time when such wx conditions would make it very difficult and unsafe to operate within the bands of the atmosphere which can support flight by aircraft of our times. It is not just convective wx that may be a problem. Increase in volcanic activity and its combined effects of spread due to strong convective atmosphere and jet stream activity that would be a major issue when such conditions become permanently established as the norm rather than the exception.
Here is the link to articles on the subject of extreme wx:
https://nca2 014.globalchange.gov/highlights/report-findings/extreme-weather#intro-section-2
Richard Branson and his Virgin Galactic may perhaps be the answer to the future of aviation.