Whenever one sees unique airlines, like Air Cambodia (or variations of the name thereof), we know it is Hajj season at DEL. Rest of the year, the Haj Terminal is used for courier operations/express cargo/special moves like U.N. etcetc.
Going back to my shippie days, Hajj pilgrim ships were the norm then. It was one big private trucking scenario for everybody, passenger/pilgrim, crew, owner/operator, flag nation, host nation . . . the works. Smuggling was the order of the day, be it gold, illegal stuff, human trading . . . nothing was haram.
I guess it hasn't changed even now, which is why the air-charterers of the world get active. I do not have any idea of the current day favourites, but presume that alcohol and weaponry would be the two big ticket items inwards and Bactrian gold as well as Iraqi antiques outwards?
That's the ground level view on the Hajj!