import math


def haversine_nm(lat1, lon1, lat2, lon2):
    # Earth radius in nautical miles
    R = 3440.065
    phi1, phi2 = math.radians(lat1), math.radians(lat2)
    dphi = math.radians(lat2 - lat1)
    dlambda = math.radians(lon2 - lon1)

    a = (
        math.sin(dphi / 2) ** 2
        + math.cos(phi1) * math.cos(phi2) * math.sin(dlambda / 2) ** 2
    )
    c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a))

    return R * c