Being vaguely aware of the software that powers the airline industry, I’m almost certain that there were some serious challenges in working on this redesign—unfortunately, it looks as though performance was one of them.

After chatting with Jake and a couple of others on Twitter, I decided to add Ryanair.com to my Calibre account to see what stats and graphs would be able to tell me.

Ouch. When I looked into the requests being made, it didn’t look as though anything unusual was happening. The site is large, but being as the industry average total page size is now well over 2000KB (as reported by httparchive), it didn’t seem completely out of control.

Webpagetest’s CPU utilisation graph showed that something much more sinister was happening.

Notice the flat line at the top of the graph? That’s the CPU being pegged at 100%.

When a site causes such signifigant CPU spikes, it could be one of a few things:

Excessive use of animation (or non-hardware accellerated animation)

Intensive JavaScript — iterating over a large DOM, audio analysis, endless loops

HD Video playback

Expensive CSS selectors targeting a large amount of DOM elements

Being that there wasn’t any obvious runtime performance issue, and we knew that the TTVC (Time to visually complete) was slow, I started to investigate the network timeline.

There was a total of 342kb of CSS being delivered over the wire using GZip. Once those stylesheets are uncompressed? Totally different story—2.88MB.