diff --git a/astroplan/plots/time_dependent.py b/astroplan/plots/time_dependent.py
index <HASH>..<HASH> 100644
--- a/astroplan/plots/time_dependent.py
+++ b/astroplan/plots/time_dependent.py
@@ -135,6 +135,7 @@ def plot_airmass(targets, observer, time, ax=None, style_kwargs=None,
         style_kwargs = {}
     style_kwargs = dict(style_kwargs)
     style_kwargs.setdefault('linestyle', '-')
+    style_kwargs.setdefault('linewidth', '1.5')
     style_kwargs.setdefault('fmt', '-')
 
     # Populate time window if needed.
Slightly thicker lines look better against shading