There is no upper age limit for starting flight training with a certified instructor. To be issued a private pilot certificate, however, you must be at least 17 years old. After you earn your private pilot rating, you may continue flying as long as you can pass the required medical exams to keep your medical certificate valid and complete a flight review every 24 months.
For airline professionals, the mandatory retirement age for commercial pilots on international flights was increased from 60 to 65. Full details of this change are outlined in HR 4343.