Https://amtrakoig.gov/sites/default/files/webform/foia_form/_sid_/air-fare-policy-what-is-the-cheapest-day-to-book-a-flight-on-lufthansa-airlines.pdf https://amtrakoig.gov/sites/default/files/webform/foia_form/_sid_/air-fare-policy-what-is-the-cheapest-day-to-book-a-flight-on-lufthansa-airlines.pdf