Hmm, I've never heard of that one! Are you using a huge, higher-than-full-HD monitor?

Try zooming into the site one or two clicks. Hold down the Command key and tap the + key once or twice. Then reload bypassing the cache (Command+Shift+r) and see whether anything changes.

I took a screen shot but for some reason Firefox will not upload it properly. This is what the error msg says:

OPS Machine’s Minimum System Requirements should be

   Operating System (OS): Windows 7
   Internet Browser: IE 9
   Screen Resolution: Greater than 1280 x 1024

• As of November 7, 2012, you will not be able to login if minimum requirements are not met.

Note to you: You may change the screen resolution limit to 1024x768 as the minimum which means that 1050x813 would be also accepted. Minimum and above to be accepted. Current System Configuration Browser name = Firefox Full version = 63.0 OS = Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:63.0) Gecko/20100101 Firefox/63.0 Your resolution is 1440x900

Okay, it seems to be:

dokbyr said

OPS Machine’s Minimum System Requirements should be ...

• Screen Resolution: Greater than 1280 x 1024

Current System Configuration...

• Your resolution is 1440x900

So they want a little more height, it seems.

Try the opposite of what I suggested before. Zoom out by holding down the Command key and tapping the - key once or twice. Then reload the page and see whether the site is fooled.

Of course, you might need a magnifying glass after that...

You know, I'm not sure what the connection is between

https://www.cheapoair.com/

and the source of that message -- OPS? Do they send you off to other sites to do the actual booking?

No goes no where. I finally gained access to the website by clicking several different places on the home page. Weird.