This past weekend I flew to Boston. I've done this many times, yet this time I experienced one of the most frustrating user experiences in a long time. This occurred when I was checking in on the porter airlines website.
I went through the various check in pages carefully inputting my information. To my surprise, on the very last page when I clicked the check in button I got the following message. "On-line check in not available for passenger (my name inserted here)." Initially I thought maybe there was an issue with their server and I tried again later. However, I got the same message again. At this point I had already spent 20 min trying to check in so I gave up.
Come the day of the flight, when I got to the airport it turns out I was randomly selected for additional security screening. Now, that wasn't an issue but the least they could do is give you the message at the start of your on-line check in. Not when you've completed the forms and are trying to submit it. They should also re-word the message as it is so vague that it only causes confusion.
Overall, they need to redesign this feature of their on-line check in as it is a really poor experience for a passenger. The majority of online check in services such as my family doctor's website indicate whether or not you can check in at the very beginning of the process. So such a design change has no downsides and porter airlines has no reason to have such a design. It's such a simple and intuitive design aspect.
To conclude, the lesson here is design the interface to be as easy and straightforward for the user as possible. Do not cut corners. Note, I have not included images of this interface issue as the page contains sensitive data. Also, I have not seen this porter airlines issue raised anywhere in my web search.