I have a raspberry-pi piaware feeder that also serves as a twitter bot that tweets when airplanes flight directly overhead (within one mile or 50 degrees from the horizon). Recently I’ve been using the flightxml 3 api (FlightInfoStatus) to get information about the flights and adding them to the tweets. It’s been working pretty well.
Unfortunately I’ve been averaging about 100-175 tweets a day, so the 1000 free requests per month get used up pretty quickly. I understand that the service is free and I can upgrade, but it would require the silver package to be fully covered and I can’t justify the $50 a month for a hobby toy 
Anyway, I’d be willing to pay something closer to 5 to 10 dollars a month if I can guarantee full coverage for the month. Maybe you can offer a tier specifically for piaware users where the request only works if it comes from the same ip address as a piaware feeder? Just an idea I thought I’d throw out.
Over all FlightXML service is pretty cool and thanks for having some kind of free tier for us plebs to use