The Air Force's $5.5 billion unfunded priorities list for fiscal year 2016 includes money for legacy aircraft upgrades and to retain force structure, but Chief of Staff Gen. Mark Welsh has cautioned lawmakers not to pursue the requests at the expense of other service priorities. According to a copy of the March 10 letter obtained by InsideDefense.com , the submission includes $2.4 billion to modernize legacy fighter, tanker, airlift and surveillance aircraft, mostly within the Air National Guard, as well...