There are several ways to book a trip with multiple airlines. 

• Search for your trip, and Perk will automatically provide results for bundled flight tickets.  
• Book a multi-city trip.
• Make one-way bookings for each airline, following the steps on Book a flight on Perk. On the Review your trip itinerary page, under What would you like to add?, click Flights.
• For complex trips, you can use the Concierge service.

Tip: Two one-way flights with low-cost airlines usually come to the same price as a return flight. Two one-way flights with regular airlines are usually more expensive than a return flight.