If you look at chart for a stock price the big picture changes as you click, 1 week, 1 month, 1 year, 5 years, etc.

For this industry a good time frame to look back would be equal to how far you have to go. If you have 30 years to go, look back 30 years and draw a trend line. If you have 5 years to go look back 5 years.

Sadly a newbie looking back 30 years has to project 30 into the future, in which case the trend is NOT your friend. There is nothing in place to reverse the trend right now but a bunch of hot air "We're Taking it back", "Fix it Now", etc. Nice but no credible action behind it.

There are several items in place or in motion to continue the trend. Further improvements in automation, NextGen ATC, MPL, Labor laws, Age 65, etc.