How was Mij to be transported to England?
Since the British airline to London would not fly animals, the author had to find an alternative route to transport his otter. He booked a flight to Paris on another airline, and from there, he would catch a connecting flight to London.
Furthermore, the airline had strict conditions for carrying the pet on board. They insisted that Mij should be packed into a box that was not more than eighteen inches square. This box was to be kept on the floor at the author's feet during the flight.
Explanation
The context explains that because the British airline refused to transport animals, the author had to book a different flight to Paris and then to London. Additionally, the alternative airline mandated that Mij be kept in a small box, measuring no more than eighteen inches square, on the floor by the author's feet.