From the airport
Public transport lines: from Linate catch the underground Metro 4 (blue line) and get off at San Babila (toward San Cristoforo). Here change with the underground Metro 1 (red line) and get off at Rho FieraMilano station.
From the Malpensa Airport
Public transport lines: Take the express train from Malpensa to Cadorna Station, then take the underground Metro 1 (red line) toward Rho Fiera and get off at the end of line. It's a 1h 45 minutes trip and is 13€ + 2.00€.
Taxi: It's a 30 minutes and costs 80€.
Aerobus shuttle: Departs every 20 minutes and costs € 10. Take the MalpensaShuttle to Central Station, then take the underground Metro 3 (yellow line) toward San Donato for 4 stops and get off at Duomo stop, change the metro line and take the metro 1 (red line) toward Rho Fiera till end of line.
From the Orio al Serio Airport
Taxi: It's a 1h 40 minutes trip and costs 130€.
Aerobus shuttle: Departs every 30 minutes and costs € 8-10. Take the OrioShuttle to Central Station, then take the underground Metro 3 (yellow line) toward San Donato for 4 stops and get off at Duomo stop, change the metro line and take the metro 1 (red line) toward Rho Fiera till end of line. The underground ticket is around 2€ per person per trip.