Fermi LAT (2-day bin, top panel) and optical light curves (bottom panel) of PKS 1424−418. The dashed horizontal line in the upper panel indicates the mean γ-ray flux over the whole observing period considered in this work. Vertical lines denote the three prominent outbursts studied in this work: black, flare A (2009 June 22−July 20, MJD 55 004−55 032), red, flare B1 (2010 May 6−16, MJD 55 322−55 332), blue, flare B2 (2010 May 19−25, MJD 55 335−55 341), and green, flare C (2011 April 19−May 16, MJD 55 670−55 697).