I believe most of the issues I have with the newish UI have already been raised. To me it seems like you tried to keep the same UI rather than implementing the key user stories in an efficient work flow. Clicking on 'flight availability' and then navigating by keyboard no longer works. I have to press tab 30+ times to get even close to the origin airport field. My 'recent alert' is from 2007. The three recent searches are a mix of search from last month (not the last ones) and one from 2016. Fonts and rendering on Firefox has numerous issues.
You seem to have a newer technology stack now. Why not build a modern UI and reconsider some of the typical work flows? I'd rather see you drop 90% of the 'content' on the site and just have a limited but effective features implemented.