If you want to upload .ipa file to itunesconnect without integrating developer account in Xcode and you want to use application loader. then you can generate .ipa with iTunes .
Step 1 :- Select device inplace of simulator.
Step 2 :- Go to Product -> select Archive
Step 3 :- After complited process right click to your Archive -> and select show in Finder
Step 4 :- when you click on show in finder you will redirect to Archive folder, looks like this
Step 5 :- Right click on .xarchive file -> select Show in finder option.
Step 6 :- Go to Product Folder -> Application Folder -> You will find yourprojectname.app
Step 7 :- Now to convert .app to .ipa just drag and drop into itunes . check below image ,
Step 8 :- Now put this .ipa file in safe place and use when upload with application loader .
Note :- if you want to know how to upload app with application loader then check this ,
WARNING :- Don't make .ipa with changing extension from .aap to .zip and .zip to .ipa.
I have seen in many answer that , they have suggest compress .app file and then change the extension from .zip to .ipa . It is not working now . By this method you will get Error like ,
IPA is invalid, it does not include a payload directory.