The active foliar area (AFA) is a key parameter in banana crop models, but it is hard to evaluate andexisting in vivo assessment models are unreliable. We studied the leaf area dynamics in 405 plantainsbelonging to nine varieties (Batard, Big Ebanga, CRBP39, D248, D535, Essong, FHIA21, French clair andMbouroukou n?3) throughout one crop cycle. An analysis of the structure of 8858 monitored leaf con-figurations (i.e. each defined by a variety, a number of living leaves and a banana development stage atthe monitoring time) revealed the leaf area dynamics versus banana development phases. This analysisalso confirmed the relevance of a linear leaf area (LA) increase model. Two ANOVAs were performed toassess the sensitivity of the linear AFA simulation model regarding the variety, number of living leavesand banana development stage at the monitoring time. Finally, we propose a new banana AFA simulationmodel based on a combination of two linear models. The OTO (for 'leaves One, Three, One') model onlyinvolves two input parameters: the number of living leaves at the monitoring time and the length andwidth of three of these living leaves. The model validation confirmed its independence from the variety,banana configuration at the monitoring time, and cropping conditions. This simple and portable tool canbe used to assess the AFA of any banana plant, irrespective of its variety, development stage and croppingconditions.