I think its completely fair that you tell your current employer you need to start looking at options and you will give them thru (example) September to assist in the transition. Interview with the understanding your start date will be October. Get a CJO (at wherever) for an October start date, if things happen faster you can always try to get an earlier class date, if things are going to take longer (say maybe a week or two), you can call the recruiter and push it out a few weeks. Keeping in mind most CJOs are only good for 6 months (not sure about Flex). Bottomline is this industry (and economy) could look completely different come October and if there is very little hiring (or layoffs/furloughs), you could end up without any flying job OR back up job all becasue you tried to help your current employer out.