So, first of all, he needs to get himself to a psychiatrist. Anxiety is something a lot of people deal with successfully without meds. However, once it has crossed into chronic panic disorder that interferes with normal life experiences, it's a pathological medical problem. It needs treatment with medication AND therapy. There are numerous medications that can alleviate these symptoms and improve mental functioning and allow your husband to live a normal, enjoyable life.
But since that's not going to help in the immediate term, here are some suggestions to cope.
1. Audio/Podcasts. If he listens to them already, great. Make sure he has a long Playlist of podcasts to listen to. There are even podcasts for anxiety and calming down. Try the Calm app for some helpful meditations to listen to when feeling overly anxious or panicky. Or go to You Tube and search "relaxing music for anxiety". You can download
YouTube videos to listen to offline. I have a relaxing sounds scape/piano music YouTube video downloaded and saved in my library. It's very helpful.
2. Peppermint oil or strong mints like altoids. A good way to overcome panic attacks is a sensory assault on another part of your body. Mints and smelling peppermint works for me. This works by literally tricking your brain into paying attention to that and focusing attention away from the negative thoughts. Other people successfully use the tapping method or the rubber band snapping method. Google these.
3. Play the 5 things game. Look around and name 5 physical attributes of 5 things you see nearby. In an airport, this might look like this: "I see a red suitcase. It's hard. It's shiny. It's small. It has a blue tag on it. I see a Starbucks coffee cup. It has a straw. It has the name John on it. It had ice cubes. It's cold."
This works like the peppermint. It gets your brain to think about something else.
4. Take magnesium supplements or stress gummies. They are calming. There are lots of brands of these in drugstores. I like Olly Stress gummies and Calm Magnesium powder. Even the airport newsstands like Hudson News sell calming supplements.
5. Arrive early enough to the airport to have time so he is not rushing. Don't drink coffee or soda (caffeine will make anxiety much worse). Don't eat a heavy meal before the flight.