Solution

Let us consider 1 as one step and 2 as two step. Consider the following conditions to reach the flight with 1 or 2.

• 1, 1, 1, 1, 1, 1, 1, 1 - This can be done in 8C0 ways = 1.
• 1, 1, 1, 1, 1, 1, 2 - This can be done in ⁷C₁ ways = 7.
• 1, 1, 1, 1, 2, 2 - This can be done in ⁶C₂ ways = 15.
• 1, 1, 2, 2, 2 - This can be done in ⁵C₃ ways = 10.
• 2, 2, 2, 2 - This can be done in ⁴C₀ ways = 1

Total number of ways = 1 + 7 + 15 + 10 + 1 = 34