I recently took a flight with Delta airlines. They offer in-flight WiFi for messenger services iMessage, Facebook Messenger and Whatsapp and state that

Words and emojis accepted. Sending photos, videos or SMS messages is not supported.

Given the encryption for these services, most popular in the news being probably Whatsapp, I am wondering how they can distinguish the different content types. Maybe a cap on message size?

Delta airlines Wifi description


  • I think it’s message sizes, or more likely - data transfer rate. – Andrew Morozko Jul 16 at 9:50
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    @AndrewMorozko this would mean that choosing an image small enough would allow transmitting it? I should try this on my next flight – Fabian Jul 16 at 9:54
  • most definitely you would be able to do it. Only images are large by default, send something like 8x8 px for testing – Andrew Morozko Jul 16 at 9:57
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    Well, consider that SMS uses a completely different service, and maybe they haven't whitelisted the gateways needed for all carrier's WiFi calling. – multithr3at3d Jul 16 at 11:32
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    @multithr3at3d to emphasize, my question is regarding the different content types per messenger. E.g. how they can allow messages to pass that contain text versus images for WhatsApp. I think it is clear that they can distinguish between the different services but what my question aims at is rather: what part of the communication can they see that gives them enough information to make this content type distinction? – Fabian Jul 16 at 11:41

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