What is the error message you get?

When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Clear Firefox's Cache

See: How to clear the Firefox cache

If you have a large hard drive, this might take a few minutes. If you do not see the number going down on the page, you can reload it using Command+r to check progress.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, try either:

• right-click (on Mac Ctrl+click) a blank area of the page and choose View Page Info > Security > "View Cookies"
• (menu bar) Tools > Page Info > Security > "View Cookies"
• click the padlock or "i" icon in the address bar, then the ">" button, then More Information, and finally the "View Cookies" button

In the dialog that opens, the current site should be pre-filled in the search box at the top of the dialog so you can remove that site's cookies individually. Or type southwest.com in the box if needed.

Then try reloading the page. Does that help?

For people wondering why Firefox 16.0.2 well that is the last Firefox Release that could run on a intel Mac with OSX 10.5. https://support.mozilla.org/en-US/kb/firefox-no-longer-works-mac-os-x-10-5

Firefox 17.0 to the current 48.0 Release will work on OSX 10.6 however the Firefox 49.0 release will require OSX 10.9 at minimum. https://support.mozilla.org/en-US/kb/firefox-osx

Hi Pete, thank for your message. I understand that after clearing cache and cookies you still get:

'The connection was reset. The connection to the server was reset while the page was loading.'

And that in Safari you get a secure connection error.

That could be the same problem, but so much has changed since Firefox 16 that I don't know what it can connect to any more.

Could you open this page -- it analyzes the various features of your Firefox's ability to make secure connections:

https://www.ssllabs.com/ssltest/viewMyClient.html

In particular:

(1) Protocols

Southwest requires TLS 1.2. Does your test page show that TLS 1.2 is supported?

(2) Ciphers

This section is hard to read, but does your Firefox list these ciphers as supported?

TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA

In Firefox 48, these are the only ciphers that Firefox and the site share in common; the site does not allow lower strength ciphers.

Info on what the server requires drawn from:

https://www.ssllabs.com/ssltest/analyze.html?d=www.southwest.com

jscher2000 said

Southwest requires TLS 1.2. Does your test page show that TLS 1.2 is supported?

TLS 1.2 support was added as of Gecko 24.0 or Firefox 24.0 as the old Firefox 16.0.2 did not support TLS 1.2.