If you can't find a single 5-minute file that fits your specific needs, download a high-quality 30-second loop from Storyblocks or Pixabay and duplicate it in any free editor like Audacity to reach your desired length. Helicopter Flight (75 Minutes) - SoundCloud
Finding high-quality, long-duration helicopter sound effects can be tricky since many stock libraries focus on short clips. For a solid 5-minute experience, you can use these verified sources for continuous flying and ambient sounds. helicopter_sound_effect_flying_5_minutes
Offers hundreds of clips, including some looping files that can be easily extended to 5 minutes. If you can't find a single 5-minute file
You can find extended clips like a 5-minute, 29-second recording of a helicopter landing with cockpit radio on HookSounds . Offers hundreds of clips, including some looping files
A massive library of specific helicopter types (Huey, Apache, etc.) for more realistic or "solid" sound design.