Aviation is a major contributor to global greenhouse gas emissions, highlighting the urgent need for behavioral interventions that encourage a shift toward more sustainable modes of transportation, such as rail travel. This research investigates how ecolabels influence travel mode decisions by promoting trains over flights. In an online experiment with a fictitious booking travel platform, 330 participants indicated their purchase intention and actual selection between three travel options: a flight (high emissions), a bus (moderate emissions), and a train (low emissions), across four experimental conditions. These included a control condition (no label), an implicit color-coded label, an explicit label informing about the CO₂ emissions, and a combined label incorporating both the implicit and explicit formats. Results indicate that the implicit label significantly decreased participants' intention and actual selection of air travel and increased their intention and choice for train travel. No significant effects were observed on bus travel choices. Furthermore, the combined label did not yield additional benefits beyond those achieved by either label alone. These findings contribute to the research on behavioral economics and environmental psychology by addressing a critical gap in understanding how labeling interventions that are effective in low-impact, low-effort contexts (e.g., food choices) affect people's decisions regarding high-impact, high-effort behavior changes, such as rethinking travel behavior.