Tripadvisor stock (NASDAQ: TRIP) surged 8% on July 2 — significantly surpassing the S&P 500's modest 0.47% increase — after activist investor Starboard Value revealed a stake exceeding 9% in the online travel company. The approximately $160 million investment caused shares to climb another 7% in after-hours trading on Wednesday.

Expedia’s stock ended the holiday-shortened session up 3.2%, its largest rise since it rose 3.8% on May 27. Tripadvisor’s stock shot up 16.7%, and has soared 34.1% over the past three sessions. Among others in the travel-services space, Airbnb Inc.’s stock was up 0.8% and Booking Holdings Inc. shares moved higher by 0.3%, at the closing bell.

Activist investor Starboard Value has built a 9% stake in Tripadvisor after the online travel-review company eschewed takeover offers in the past year.The detailsStarboard, the investment firm run by Jeff Smith,