My Delta planes have disappeared!!

Hi,

I'm at level 25. I just did some expanding. I purchased two Delta jets and ran them for about a week. Last night I went to play and they were gone, replaced with turbo props. What the heck is going on??
Please help.

Defrasier

iOS Game?

have a look here - https://airportcity.forumotion.com/t425-new-update-planes-change