Age is visible in the maintenance view after the last round of updates (see changelog). (can't fit all info into the one view)
If noise chapter and age are both visible in maintenance view, that's fine and solves the issue, but that's not the case. Age IS needed in maintenance as it helps to know which planes to scrap when you're sorting by D check, etc., so leave that one alone.
Back to the technical view though - there's still a usability issue for the real world game play examples.
1. Well crap, noise regs are in play, which bleeping plane is grounded? Solved with sorting by noise on tech page. (OK)
2. Noise regs are coming soon and I plan on flying all planes younger than 20 years into the noise reg era, I need to apply hushkits to those planes as the rest will be scrapped. I also don't want to do every plane at one time for operational/competitive purposes. Not solved.
Suggestion: Since condition is already in the maintenance view, nuke it from the technical view and put age back. I can't think of a use case where I want to do anything more complicated than sorting by condition to determine where the technical problem delays are coming from.