\batchmode
\documentclass{jasatex}
\usepackage{fontspec}
\setmainfont[Mapping=tex-text]{FreeSans}
\setsansfont[Mapping=tex-text]{FreeSans}
\setmonofont{FreeSans}

\begin{document}

\title{Manuscript Title}
\maketitle

\section{Introduction}

\begin{figure}
\end{figure}

\end{document}