I didn't know that I needed until the customer service lady told me. And it's a bit ridiculous to have to download an entire new browser just to buy a united airlines ticket.

As I previously said, I have over 250,000 United miles, I have flown on them a great deal and the issue with Safari hadn't previously come up. I don't know why it is now. However, after researching the issue United has had multiple problems with Safari since 2014.