As the title says, I was scheduled to fly CA901 on 23 May, but the flight was delayed by roughly 10 hours. I ended up bailing on the flight altogether. I tried looking it up on EF to figure out the reason, but couldn't find anything. The GA said it was due to weather, but there were no weather advisories for either PEK or ULN that day. In addition, OM224 was also delayed by 9-10 hours that day. I've also noticed that CA901 has been similarly delayed several other times in the past week.

Any idea what's going on here?