"download: yes or no’?"
Not over the Internet, no. No way. Not in a million years.
I do hope this download functionality means from a secure site to a local, secure server, then control and validation of the package and then distribution to the planes via sneakernet.
The last thing you want for multi-million dollar jets is to let them open to man-in-the-middle attacks and all the other joys of Internet insecurity. The only way to be sure that these very expensive tools are not vulnerable is to not have them link up.
Period.