Clean up audio: Interviews inside plane w/ loud engine noise

I need about 60 seconds of interviews cleaned up. They're interviews conducted inside a small airplane, and have a loud engine noise in the background. I recorded it with noise-canceling headphones but the engine sound is still loud and bothersome. It's a static low-frequency hum. I'd like both the engine sound brought down, and the human voices amped up. However, if cleaning up the background engine noise is impossible, I'd like the voices brought up significantly so I can hear it clearly, without it sounding like a robot. Here is a sample audio clip: [login to view URL] Please only bid if you are certain you can clean it up without distorting the audio. Please also let me know what you are capable of (i.e. Can you reduce both the bkgd noise AND amp up the voice, or can you just amp up the voice?) Thank you!!!!!