Vail, who prior to his appointment was planning director at Saatchi & Saatchi, overseeing T-Mobile Europe and Dr. Martens, will become senior strategic planner.
Howard and Vail will report to Dave Cobban, planning director at W&K Amsterdam. Cobban said: "Jenny and Jonas are critical hires for us because they both bring with them experience of interactive and integrated planning.
"They fit seamlessly into our planning department because we operate a structure where communications and strategic planning work symbiotically on all client briefs."
The appointments come in the wake of several major account wins across the W&K network. In July, the independent network was selected as Nokia's lead agency on its global strategic and creative account.
The Nokia win came on hot on the heels of W&K London's appointment to develop Visa's global Fifa World Cup sponsorship campaign.
Howard said: "I was keen to take a role whereby communications planning would be considered right at the start of the process. Communications planning isn't a separate department here but simply one specialty within the planning department."
Jonas said: "The strategic and communications planners work together here at W&K Amsterdam, like the creative pairing of art director and copywriter. Each brings a different but complementary perspective to the brief from day one."