Ottawa MacDonald-Cartier International Airport
The state-of-the-art Ottawa MacDonald-Cartier International Airport is 15km south of the city and, perhaps surprisingly, is very small. Almost all international flights require a transfer before arriving in the capital (normally in Toronto's Lester B Pearson International Airport). Nonetheless, numerous North American carriers serve the airport, including Air Canada, WestJet, Porter Airlines, United Airlines, Delta and American Airlines.
The cheapest way to get to the airport is by city bus. Take bus 97 from Slater St between Elgin St and Bronson Ave (make sure you are heading in the 'South Keys & Airport' direction). The ride takes 40 minutes and costs $3.65.
Ottawa Shuttle Service offers private and shared shuttles from downtown hotels.
Blue Line Taxi and Capital Taxi offer cab services; the fare to/from downtown is around $30. During the week, if you're having a hard time snagging a cab, there's always a cluster on Metcalfe St between Sparks and Queen Sts.
Car & Motorcycle
Major car-rental chains are represented at the airport and offer several locations downtown, on Catherine St and at the train station (both just off Hwy 417). You will likely get a better deal hiring a car in Toronto.
The VIA Rail Station is 7km east of downtown, near the Hwy 19/Riverside Dr exit of Hwy 417. Trains run to Toronto ($108, 4½ hours, eight daily) via Brockville and Kingston, and to Québec City via Montréal ($62, two hours, six daily).