The goal of this randomized controlled clinical trial is to test a 12-week physical activity telecoaching program for NSCLC patients after surgery. The main question it aims to answer is: What is the effectiveness and acceptability of a 12-week (semi)automated low-to-moderate intensity PA tele coaching program on physical activity (mean steps per day) in resectable (stage I-IIIA) NSCLC patients after lung surgery, as compared to usual care? Patients with NSCLC will be enrolled in the study from 1 month postoperatively up to 1 year postoperatively. They will be randomized in either the intervention group or the control group. Patients randomized in the intervention group will be asked to enter a 12-week physical activity telecoaching program with the aim to enhance their physical activity. The telecoaching programs consists of 4 pilars: 1. A wearable (Fitbit) to measure and give feedback on their daily step count. 2. A smartphone coaching application, installed on a smartphone and linked to the wearable, providing automated coaching by displaying an individual activity goal (expressed as daily step count) and daily and weekly feedback on the performance (steps) of the patient. 3. A one-to-one semi-structured interview with the coach discussing the importance of physical activity, motivation, self-efficacy, barriers, favourite activities, and (coping) strategies to become more active resulting in an individual action plan. 4. Phone calls by the coaches initiated in pre-defined situations (non-compliance with wearing the step counter, failure to transmit the data, failure to progress). Patients randomized in the control group will remain their usual care and will not enter the 12-week physical activity telecoaching program.