<Page> EXHIBIT 5.6 SIMPSON THACHER & BARTLETT LLP 10 UNIVERSAL CITY PLAZA, SUITE 1850 LOS ANGELES, CA 91608 (818) 755-7000 ------ FACSIMILE: (818) 755-7009 November 10, 2003 Re: Sierra Wireless, Inc. Registration Statement on Form F-10 (No. 333-110219) Sierra Wireless, Inc. 13811 Wireless Way Richmond, British Columbia Canada V6V 3A4 Ladies and Gentlemen: We have acted as United States counsel to the underwriters in connection with the filing of a registration statement on Form F-10, as amended (the "Registration Statement"), with the Securities and Exchange Commission for the registration of the Company's common shares. In connection with that registration, we consent to the reference to our firm under the heading "Legal Matters" in the Registration Statement. Yours truly, /s/ Simpson Thacher & Bartlett LLP NEW YORK LONDON HONG KONG TOKYO PALO ALTO